[填空题]
Note: In this question, e3 c uvy2;x *;hpy,jnidisdm6 nsv:txj/ (zj umt y0m.;z8tance is in metres and time is in seconds.
A tennis ball is thrown in the air. Its height h above the ground after time t is given by
h(t)=-5 $t^{2}+20 t+4$,$ \text { for } 0 \leq t \leq 4 $.
1. Find $h^{\prime}(t)$ .
2. Find the maximum height attained by the ball.
