Explanation:
The T-shirt is launched with an initial upward velocity of 60 ft/s from a height of 5 feet. Its equation of motion is given by :
....(1)
(a) For maximum height, put

So,

Now put,

So, the time taken for the T-shirt to reach maximum height is 2.5 seconds.
(b) Put x = 2.5 s in equation (1)