In the Soapbox Derby, young participants build nonmotorized cars with very low friction wheels. Cars race by rolling down a hill. The track at Akron's Derby Downs, where the national championship is held, begins with a 55- ft ~long section tilted 13° below horizontal.

a. What is the maximum possible acceleration of a car moving down this stretch of track? 

b. If a car starts from rest and undergoes this acceleration for the full 55 ft, what is its final speed in m/s?