Suppose a 32-pound weight stretches a spring 2 feet. If the weight is released from rest at the equilibrium position, find the equation of motion x(t) if an impressed force f(t) = 24t acts on the system for 0 ≤ t < 5 and is then removed (see Example 5 in Section 7.3). Ignore any damping forces. (Use g = 32 ft/s2 for the acceleration due to gravity.)