Optimization/Minimizing Total Expense

A truck driving on the Interstate averages a fuel efficiency of 4 miles per gallon when traveling at 50mph.  The truck looses a tenth of a mile per gallon in fuel efficiency for each mile per hour increase in speed.  Fuel costs $1.19 per gallon.  The trucker is paid $27.50 per hour and fixed costs to run the truck are $11.33 per hour.  A trip of 300 miles is planned.  What speed will minimize the company's total operating expense?