A skier with a mass of 72 kg starts from rest and begins to move downhill with a net force of 90 N [forward] for 7.9 seconds. The hill levels out for 3.5 seconds. On this portion of the hill, the net force on the skier is 22 N [backwards]. a) Calculate the velocity of the skier after 7.9 seconds. [1T/1C/2A] b) Calculate the velocity of the skier at the end of the section where the hill levels out. [1T/1C/2A]