Final answer:
The marginal product of the third painter is the additional area painted due to the third painter's efforts, which is 75 square feet per hour beyond the 200 square feet painted by the first two painters.
Step-by-step explanation:
To calculate the marginal product of the third painter, we need to determine the additional output produced by the third painter after the output provided by the first two painters has been taken into account. With two painters, the output is 200 square feet per hour. With three painters, the output increases to 275 square feet per hour.
The additional output provided by the third painter, which is the marginal product, can be calculated by subtracting the output of two painters from the output of three painters:
Marginal Product of the Third Painter = Output with Three Painters - Output with Two Painters
Marginal Product of the Third Painter = 275 sq ft - 200 sq ft
Marginal Product of the Third Painter = 75 sq ft
Therefore, the marginal product of the third painter is 75 square feet per hour.