1a) Just plug in x=0 and compute C(x=0). This is your cost when no units (x=0) are sold.
C(x) = 100x + 2000
C(x=0)= 100*0 + 2000 = 2000
1b) Plug x=10 into the cost equation. This is the cost when 10 units (x=10) are sold.
C(10) = 100*10 + 2000 = _______
1c) Plug x=10 into the price equation, p(x). This is the unit price when 10 units (x=10) are sold.
p(10) = 550 - 10*10 = _______
1d) Revenue, R(x), is the unit price (p(x)) times the number of units sold (x):
R(x) = p(x)*x = (550 - 10x)*x = 550x - 10x2
Problem 2 works just like problem 1. Try it on your own.