Astone is thrown upward from ground level. with what minimum speed should the stone be thrown so as to reach a height of 49 feet?

The correct answer of the given question above would be 8ft/sec. The minimum speed that the stone be thrown so as to reach a height of 49 feet is 8ft/sec. Consider this given solution here:
u^2 = 2x a x 1 
u^2 = 2 x 32 x 1 
u = 8 ft/sec
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