A person standing on the ground outside a building throws a set of keys directly upward to a person standing on a second-floor balcony. The person on the ground releases the keys with an initial vertical velocity of 28 ft/s from a height of 4 ft. The function h(t) = 16t^2 + 28t +4 models the height (in feet) of the keys at time t (in seconds) after the keys are thrown. The person standing on the balcony can catch the keys once they reach a height of 12 ft. For what period of time are the keys high enough to be caught?

a [0,1.88]
b[0.36,1.39]
c[0,0.36] U [1.39,1.88]
d(-∞,0.36] U [1.39,∞)