A projectile is launched from the ground with an initial velocity of 80 feet per second at an angle of 45 degrees with the horizontal. The height \( h \) (in feet) of the projectile as a function of time \( t \) (in seconds) is given by the equation \( h(t) = -16t^2 + 80t \). Determine the number of whole seconds the projectile remains in the air before hitting the ground. Let's think step by step and output the final answer within \boxed{}.
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