No idea where to start

Question

The cost in dollars of producing x units of a particular camera is C(x) = x2 - 10000. (10 points)
Find the average rate of change of C with respect to x when the production level is changed from x = 100 to x = 101. Include units in your answer.
Find the instantaneous rate of change of C with respect to x when x = 100. Include units in your answer.

Answer 1

Just like taking slope

C(101) = 101^2 - 10000 = 201
C(100) = 100^2 - 10000 = 0

average rate of change = (201-0)/(101-100) = 201

instantaneous rate of change
= 2x
at x = 100
rate = 200