Im having trouble with filling in a table for MC TC and AC given a cost funchtion

Question

The cost functon is C(q)= 50+.5q

im given q 1 through 7
Ive aready calculated TC for q=1 TC=50.5 for q=2 TC=51 and so on

MC is where im having Trouble.
i know MC = dC(q)/dq or change in cost over change in q.

my teacher is telling me that the MC for q=2 IS 51/2=25.5 But wouldnt MC= .5/1 ( 51-50.5)/(2-1) I cant get him to respond to my emails and im panicing

Thanks

Answer 1

It would help if you told us what MC, TC and AC mean. Marginal, total and average cost? It looks like your C(q) is already a total cost.

The marginal cost is the cost of making one more. That is clearly 0.5 here.