At an airport, its costs $7 to park for up to one hour and $5 per hour for each additional hour. let x represent the number of hours parked. write a function that models the cost, c(x), of parking x hours, where x is an integer greater than 1.
a: c(x)=5x+12
b: c(x)=5(x+1)+7
c: c(x)=5(x-1)+7
d: c(x)=5x+7