Answer:
C
Explanation:
Given y = amount of money spend for the long distance plan per month
and x = minutes used each month
Note these 2 plans are in per month basis.
Plan A: Flat $5 + $0.99 Per min used (variable cost)
transform into an equation:
y = 0.99x + 5
Plan B: Flat $10 + $0.79 per min used (variable cost)
transform into equation:
y = 0.79x + 10
Put these 2 equations together, will give you the answer as C.