Solve the all parts of given problem:
Problem: Suppose a car travels 108 km at a speed of 40.0 m/s, and uses 2.10 gallons of gasoline. Only 30% of the gasoline goes into work done against friction. (The energy content of gasoline is 1.3 x 108 J per gallon.)
Part A: What is the force of friction?
Part B: If friction is directly proportional to speed, how many gallons will be used to drive 108 km at a speed of 28.0 m/s?
Please show all work and steps I am really trying to learn this for my test.