When Going More Than 38 Miles Per Hour, the Gas $y=43.81-0.395 x$

When going more than 38 miles per hour, the gas mileage of a certain car fits the model $y=43.81-0.395 x$ where $x$ is the speed of the car in miles per hour and $y$ is the miles per gallon of gasoline. Based on this model, at what speed will the car average 15 miles per gallon? (Round to nearest whole number.)

A) 98 miles per hour
B) 73 miles per hour
C) 48 miles per hour
D) 149 miles per hour