The cost C
, in £, of a monthly phone contract is made up of the fixed line rental
L
, in £, and the price
P
, in £ ,of the calls made. Enter a formula for the cost and, enter the cost if the line rental is £20 and the price of calls made is £12.

For problems 7–10, state a reasonable domain for the problem statement, find the inverse function f –1(x), and identify the independent and dependent quantities of the inverse. 7. gary is jogging. the total distance he has traveled, in miles, can be estimated using the function f(x) = 9x, where x is his jogging time in hours. 8. camryn sells computers. she earns commission for her computer sales plus a fixed wage for each day she works. her daily earnings, in dollars, can be estimated using the function f(x) = 0.15x + 50, where x represents her computer sales in dollars. 9. the distance a motorboat travels, in meters, can be estimated using the equation f(x) = 1.9x2, wherexisthetimeinseconds, for0≤x≤10. 10. a rock band is selling tickets to a concert at a theater. the band earns money for each ticket sold, but has to pay some of the earnings to the theater. the total money earned by the band can be estimated using the function f(x) = 7.5x – 300, where x is the number of tickets sold.