The total cost (in dollars) of producing x golf clubs per day is given by the formula

C(x)=500+100x−0.1x2.

(A) Find the marginal cost at a production level of x golf clubs.
C′(x) =

(B) Find the marginal cost of producing 35 golf clubs.
Marginal cost for 35 clubs =

2 answers

you have the functions. Just plug in the values.
dC/dx = 100 - .2 x

at x = 35
dC/dx = 100 - 7 = 93 dollars per club at a level of 35 clubs

by the way total C for 35 clubs = 3877.5 or about an average of 111 dollars per club