A ball is dropped from a boat so that it strikes the surface of a lake with a speed of \( 16.5 \mathrm{ft} / \mathrm{s} \). While in the water, the ball experiences an acceleration of \( a=10-0.8 v \), where \( a \) and \( v \) are expressed in \( \mathrm{ft} / \mathrm{s}^{2} \) and \( \mathrm{ft} / \mathrm{s} \), respectively. The ball takes 5.100 s to reach the bottom of the lake.