[填空题]
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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.
