An object thrown or fired straight upward at an initial speed of v0 ft/s will reach a height of h feet after t seconds, where h and t are related by the formula h = −16t^2 + v0t. Suppose that a bullet is shot straight upward with an initial speed of 400 ft/s. (a) When does the bullet fall back to ground level?
(b) When will it be at a height of 5200 ft?
(c) When does it reach a height of 1.8 miles?
(d) How high is the highest point the bullet reaches?