Refer to Example 9. After how many seconds will the rocket be

(a) 240 ft above the ground? 

(b) 112 ft above the ground?

Data from in Example 9

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EXAMPLE 9 Using a Quadratic Function in an Application If a small rocket is launched vertically upward from ground level with an initial velocity of 128 ft per sec, then its height in feet after t seconds (if air resistance is neglected) can be modeled by the function h(t) = 16t² + 128t. After how many seconds will the rocket be 220 ft above the ground?