Final answer:
There is no order size in the interval (3, 6) where the rate of change of the cost is 0.
Step-by-step explanation:
To verify C(6) - C(3), we need to substitute the values of x into the function C(x) = 10:
C(6) = 10(6) = 60
C(3) = 10(3) = 30
Therefore, C(6) - C(3) = 60 - 30 = 30.
According to Rolle's theorem, the rate of change of the cost must be 0 for some order size in the interval (3, 6). To find that order size, we need to find the first derivative of the function and solve for x when the derivative equals 0:
C'(x) = 10
Setting C'(x) = 0:
10 = 0
There is no solution to this equation because 10 is not equal to 0.