__Build the cost function C(b) where b is the number of bags of pretzels:__

C(b) = Cost per bag * b + Fixed Costs

C(b) = 0.70b + 1100

__Build the revenue function R(b) where b is the number of bags of pretzels:__

R(b) = Sale price * b

R(b) = 1.80b

__Build the revenue function P(b) where b is the number of bags of pretzels:__

P(b) = Revenue - Cost

P(b) = R(b) - C(b)

P(b) = 1.80b - (0.70b + 1100)

P(b) = 1.80b = 0.70b - 1100

P(b) = 1.10b - 1100