Flight of a Rocket. Suppose the altitude (in metres) of a rocket t seconds into flight is given by f(t) = -2+3 + 24+2 - 72t + 90 The interval where f(t) is concave down is O ( -00, 00 ) O ( - 00 , 2 ) U ( 6 , 00 ) O ( -00 , 4 ) O none of the other answers 0 4, 00 O ( 2 , 6 )