Please code using C++ and only use the header <iostream>. The use of any other headers will not be accepted. Thank you. **Title: Understanding PGandE.cpp for Energy Cost Calculation****Introduction**This document explains the structure and calculation parameters used in a programming context to compute energy charges. It uses two main categories of energy: Gas and Electric, each with its own tier pricing structure. **Gas Pricing Structure**1. **Tier 1 Quantities**: 10.1 therms2. **Tier 1 Price**: $1.415 per therm3. **Tier 2 Price**: $1.932 per therm**Electric Pricing Structure**1. **Tier 1 Quantities**: 558 kWh2. **Tier 1 Price**: $0.223 per kWh3. **Tier 2 Price**: $0.281 per kWh**Programming Function Declaration**A function named `charges` is used to calculate the cost based on the tiered pricing model:```cppdouble charges(double, double, double, double);```**Parameters**- **Amount Used**: The total energy consumed.- **Tier 1 Amount**: The baseline amount where Tier 1 pricing applies.- **Tier 1 Price**: Cost per unit within Tier 1 quantity.- **Tier 2 Price**: Cost per unit beyond Tier 1 quantity.**Explanation of Parameters**- The **first parameter** denotes the total amount of energy (gas or electric) consumed.- The **next three parameters** represent the Tier 1 quantity, the price at Tier 1, and the price at Tier 2, respectively.- This function can calculate charges for both gas and electricity by substituting the respective parameters.This structured approach allows for precise cost estimation based on actual consumption against tiered pricing schemes, facilitating better energy management and budgeting. ### Educational Website Content**Title: Understanding Gas and Electric Billing with Tiered Pricing****Introduction:**In this lesson, we'll explore how tiered pricing works for gas and electric bills. You'll learn how different levels of usage are priced and how computing charges can be effectively streamlined using programming.**Gas and Electric Billing Structure:**- **Tier Levels:** - **Gas:** - Tier 1: 10.1 therms - Tier 1 Price: $1.415 per therm - Tier 2 Price: $1.932 per therm - **Electric:** - Tier 1: 558 kWh - Tier 1 Price: $0.223 per kWh - Tier 2 Price: $0.281 per kWh**Objective:**The goal is to write a program that processes starting and ending readings for gas and electric meters. This program should calculate the charges to the nearest cent using a single function to handle both gas and electric charges, thereby reducing redundancy in calculations.**Conclusion:**Understanding tiered pricing and implementing efficient billing calculations are crucial skills in energy management and software development. By using a unified function approach, you can streamline processes and ensure accurate billing.

The main object of the program is to read the starting reading gas consumption and ending reading gas consumption value. Then call the function, calculate that takes the number of therms consumed, tier1 quantity, tier1 price, and tier2 price as input arguments. Then calculate the charges for gas consumption. Then print the amount of the charge in the main function. Then, prompt the user to enter the starting reading of electric consumption. Then, call the calculate function that calculates that takes the number of electric kWh units consumed, tier1 quantity, tier1 price, and tier2 price as input arguments. Then calculate the charges for gas consumption. Then, print the charges for units on the c++ console output window.C++ source code of the program to calculate gas and electric charges for consumption of gas and electricity. //PGandE.cpp#include<iostream>using namespace std;/*function calculate takes four arguments of double type variables as input arguments and then calculate the charges for the used quantity.*/double calculate(double used, double tier1quantity, double tier1price, double tier2price){ double charges=0; //check if used is below tier1quantity if(used<tier1quantity) { charges=used*tier1price; } else { charges=tier1quantity*tier1price+(used-tier1quantity)*tier2price; }//end of else case return charges;}//end of the function, calculate //start of main function int main(){ //Set constants for gas const double TIER1_GAS_QUANTITY=10.1; const double TIER1_GAS_PRICE=1.415; const double TIER2_GAS_PRICE=1.932; //Set constants for electric const double TIER1_ELECTRIC_QUANTITY=558; const double TIER1_ELECTRIC_PRICE=0.223; const double TIER2_ELECTRIC_PRICE=0.281; //declare double variables double startingGas; double endingGas; double startingElectric; double endingElectric; //Read values from user cout<<"Enter starting gas( /therms) : "; cin>>startingGas; cout<<"Enter ending gas( /therms) : "; cin>>endingGas; double consumed=endingGas-startingGas; cout<<"Gas price,$ " <<calculate(consumed, TIER1_GAS_QUANTITY, TIER1_GAS_PRICE, TIER2_GAS_PRICE)<<endl; //Read values from user cout<<"\nEnter starting Electric( /kwh) : "; cin>>startingElectric; cout<<"Enter ending Electric( /kwh) : "; cin>>endingElectric; consumed=endingElectric-startingElectric; cout<<"Electric price,$ " <<calculate(consumed, TIER1_ELECTRIC_QUANTITY, TIER1_ELECTRIC_PRICE, TIER2_ELECTRIC_PRICE)<<endl; system("pause"); return 0;}Screenshot of the program output: