An astronaut on the moon throws a baseball upward. The astronaut is 6​ ft, 6 in.​ tall, and the initial velocity of the ball is 30ft per sec. The height s of the ball in feet is given by the equation s equals negative 2.7 t squared plus 30 t plus 6.5​, where t is the number of seconds after the ball was thrown. Complete parts a and b. a. After how many seconds is the ball 16ft above the​ moon's surface?