Solve the problem.
-Suppose that the dollar cost of producing $x$ radios is $c ( x ) = 400 + 20 x - 0.2 x ^ { 2 }$. Find the marginal cost when 40 radios are produced.
A) $36
B) $880
C) -$880
D) $4

Question

Quizplus · Accepted Answer

The marginal cost is given by the derivative of the cost function. 
$c'(x) = 20 - 0.4x$
Substituting x = 40, we get:
$c'(40) = 20 - 0.4(40) = 4$
Therefore, the marginal cost when 40 radios are produced is $4. Hence, the answer is (D).

Solve the Problem xxx Radios Is c(x)=400+20x−0.2x2c ( x ) = 400 + 20 x - 0.2 x ^ { 2 }c(x)=400+20x−0.2x2

Solve the Problem $x$ Radios Is $c ( x ) = 400 + 20 x - 0.2 x ^ { 2 }$