Refer to Figure 18-1. Suppose the firm sells its output for $10 per unit, and it pays each of its workers $400 per week. When the number of workers increases from 4 to 5, the a. marginal revenue is $450 per unit of output, and the marginal cost is $400 per unit of output.b. value of the marginal product of labor is $3,900, and the marginal cost per unit of output is $400.c. value of the marginal product of labor is $450, and the marginal cost per unit of output is about $8.89.d. firm's profit increases.Please explain why the answer is c. The image displays a graph with a labeled curve depicting a relationship between variables $ L $ and $ Q $.### Graph Description:- **Axes:** - The horizontal axis (x-axis) is labeled $ L $, which could represent a variable such as labor units, quantity, or any logical measure in a given context. The values marked on this axis range from 0 to 6. - The vertical axis (y-axis) is labeled $ Q $, possibly denoting output, quantity, or another dependent variable. The values range from 0 to 420, with specific intervals marked at 120, 210, 285, 345, 390, and 420.- **Curve:** - The graph features a smooth, upward-sloping curve, indicating a positive relationship between $ L $ and $ Q $. - Several data points along the curve are marked with coordinates approximately at (1, 120), (2, 210), (3, 285), (4, 345), (5, 390), and (6, 420).- **Grid Lines:** - Horizontal and vertical dashed lines provide a clearer reference for each point on the curve.This graph is likely representing a scenario where increases in $ L $ lead to increases in $ Q $, illustrating concepts such as marginal productivity or other economic principles where input and output relationships are analyzed.

Given the graph, one unit increase in labor ie from 4 to 5, increases the output of 390-345=45 Marginal revenue product of labour= Marginal product* price =45*10 =$450. In other words it is the revenue that hiring an additional labor can generate. The marginal cost per unit would the cost of hiring an additional labor divided by the number of units he produces. Given the wage per week of a labour is $400 and the addition output of the worker is 45, this would help calculate the per unit cost of production ie Marginal unit per cost =$400/45=$8.89 This means it takes a cost of $8.89 for the firm to give as wage to the worker to produce a unit who produces 45 units of the good. Hence the answer is C) Marginal product is $450 and marginal cost per unit output is $8.89.