comparison of two functions in a word problem, grade 10?

Ok, so how these two different functions? why would we function will be better than the other to be used for carpooling? f (x) = -0.8 (x-0.1) and f (x) = 0.8 (x 0.1) have the graphics look the same? f (x) is the fee paid for the house to school and back in $ x is the distance in km to return home

The lines are parallel since f (x) = -0.8 (x-0.1) is negative and f (x) = 0.8 (x 0.1) is positive. The lines would be next to each other but do not intersect.