Hi could you please answer all parts to this question clearly thank you

46. Roller coasters use some of the most sophisticated technology. Safety is a big part of that technology. One of the reasons roller coasters require such sophisticated safety computers is for insurance and legal purposes. During the 1920s, 30s and 40s, roller coasters had a reputation of being wild, rough and very dangerous. They pulled up to 12 Gs (about 120 m/s2), which often snapped peoples' necks! They also tended to derail and ram into each other. Modern day coasters are practically run by computers! Computers are so important for the safety of roller coasters, they make riding a coaster safer than walking across the street! Computer calculations make it possible to dip, loop and nearly scare you to death without harming you. In testing a model of a looping roller coaster, an engineer observes that the current design would result in a zero normal force acting on the passengers at the top of the loop. (a) If the radius of the loop is 4.0 m, what is the speed of the model coaster at the top of the loop? (T-3) (b) Explain why and how the coaster design should be changed.(T-3, C- 2)