ok ive always had trouble with these sort of problems, if someone can help please, i in a hurry as well thanks

a grapefruit is tossed straight up with an initial velocity of 50 ft/sec. the grapefruit is 5 feet above the ground when it is released. its height at time t is given by

y = -16t^2+50t+5

how high does is go before returning to the ground?