....A frictionless spring with a 5-kg mass can be held stretched 1.2 meters beyond its natural length by a force of 90 newtons. If the mass begins at its equilibrium position, but an upward push gives it ar initial velocity of 2.5 m/sec, find the position of the mass after t seconds (where the upward direction is presumed to be positive). Express your solution as a real-valued function. Use g 9.8-m, as needed. sec meters