Ahelioopter is rising straight up in the air. Its distance from the ground t seconds after takeoff is s(t) feet, where stt) = 4? +16t. (a) How long will it take for the helicopter to rise to 48 feet? (b) Find the velocity and acceleration of the helicopter when it is 48 feet above the ground. n--~{:>- (a) The time it will take for the helicopter to rise to 48 feet is 2 seconds. (b) When the helicopter is 48 feet above the ground. its velocity is [3 feet per second