A parking garage is changing its parking fees for a week long festival. The function below represents the cost to park in the garage as a function of time (days into the festival).

Piece wise
c(t) =
10; 0 <= t <= 2
10; 2 < t <= 5
7; 5 < t <= 7
a) What would be the best days to park in the garage?
b) calculate c(4) - c(2)