#### Answer

The equation for the function is b(d) = 45.60 + 42.95d
For 9 days the agency will charge you $432.15

#### Work Step by Step

1. The equation b(d) = 45.60 + 42.95d was founded by adding up the cost of the daily rental fee for the car and the GPs which is 29+13.95 = $42.95 per day. This fee becomes the daily rate and so we can refer to it as our slope. We also have to add the one time fee for the fuel which is 3.80 per gallon and the car can hold 12 gallons so we have to pay 3.80(12) = 45.60 dollars upfront. The fee for the fuel is added in the equation but not multiplied by the number of days because it doesn't depend on the number of days.
2. To find the cost of bill after 9 days we just plug in b(9) in the equation.
b(9) = 45.60 + 42.95(9) = 45.60 + 386.55 = 432.15 dollars