A ball is thrown from the top of a 50-meter high building with an initial velocity of 20 meters per second. The height \( h \) of the ball above the ground after \( t \) seconds is given by the equation:
\[ h(t) = -5t^2 + 20t + 50 \]
How long will it take for the ball to hit the ground? Let's think step by step and output the final answer within \boxed{}.
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