3. A ball is thrown up into the air, its height h, in metres, after t seconds is \( h = - 4.9 t ^ { 2 } + 38 t + \) \( 1.75 \) .
a) What is the height of the ball after \( 3 s \)
b) For what length of time is the ball above \(50 m \) ?
c) When does the ball strike the ground?