what is this answer

Question

find the marginal cost per find unit at production level of 100 units.

c(x)=1200+x/10+x^2/10000

Answer 1

Cost = C(x) = 1200 + (1/10)x + (1/10000)x²

Marginal cost = C'(x) = 1/10 + (1/5000)x

When x = 100, marginal cost = 1/10 + 10/50 = 3/10