When driving at $60$ mph, a certain car gets $27$ mi/gal with the air conditioning off and $25$ mi/gal with the air conditioning on.

1. If gas costs $$1.59\frac { 9 } { 10 }/\text{gallon}$, how much does it cost per hour to run the air conditioner?

   Hint (a):

   cost of running AC = cost of running car with AC – cost of running car without AC

   Step (a):

   $\text{cost with AC: }\frac{60\text{ mi}}{\text{h}}\cdot\frac{1\text{ gal}}{25\text{ mi}}\cdot\frac{1.599}{\text{gal}}$

2. If a car drives at a rate of $x$ mi/h, it gets m mi/gal with the air conditioning off and $n$ mi/gal with the air conditioning on. If gas costs $$g$ per gallon, how much does it cost per hour to run the air conditioner?

   Step (b):

   $\text{cost with AC: }\frac{x\text{ mi}}{\text{h}}\cdot\frac{1\text{ gal}}{n\text{ mi}}\cdot\frac{g}{\text{gal}}$