c = f + n v
or
cost = fixed + variable * number
that is a straight line
with slope v and c intercept f
1100 = f + (500) v
1400 = f + (650) v --subtract----
-------------------
-300 = -150 v
v = 2
then
100 = f
so
c = 100 + 2 n
if n = 1000
c = 100 + 2000 = 2100
ANSWER IS:A
