A ball is thrown from an initial height of 7 feet with an initial upward velocity of 28/fts . The ball's height h (in feet) after t seconds is given by the following. =h+7−28t16t2 Find all values of t for which the ball's height is 15 feet. Round your answer(s) to the nearest hundredth. (If there is more than one answer, use the "or" button.)