Some Major League Baseball pitchers can throw a fastball at speeds of up to and over 100

Question:

Some Major League Baseball pitchers can throw a fastball at speeds of up to and over 100 miles per hour. Assume a Major League Baseball pitcher throws a baseball straight up into the air at 100 miles per hour from a height of 6 feet 3 inches.
(a) Use the position equation to write a mathematical model for the height of the baseball.
(b) Find the height of the baseball after 4 seconds, 5 seconds, and 6 seconds. What must have occurred sometime in the interval 4 ‰¤ t ‰¤ 6? Explain.
(c) How long is the baseball in the air?
Use the position equation given in Example 8 as the model for the problem.