Lab Functions 2 Topics covered: C++ Program Development Practice, Loops, Functions and Arrays Lab Elements A. Factorial Calculation Use filename: factorial.cpp write a function that computes the factorial for given integer value by loop iteration. Note - for a given number n, its factorial value is given by n! = 1*2*3*...*(n-1)*n By definition, 0! = 1! = 1 The function prototype is given by int factorial(const int &); Function should do following tests on argument value: • If argument < 0, return -1. After the function returns, your main() should check the return value. If return value == -1, output an error message and halt program execution by using the statement: return 1; The code in main() would look something like - int factorialValue if(factorialValue == -1) { factorial(-1); // trying to compute (-1)! %3D cout « "Error: factorial value for negative number is not defined" <« endl; return 1; If (argument==0) || (argument==1), immediately return 1; • For argument > 1, compute its factorial by iteration and return factorial value