A trebuchet hurls a large stone at a castle wall. The quadratic function describing the path of the stone is y = 4.9x 2 + 20x + 5, where y represents the height, in metres, of the stone above the base of the trebuchet and x represents the time, in seconds, the stone is in the air. Use your graphing calculator to answer the following questions to two decimal places.

a. What is the maximum height of the stone above the base of the trebuchet during the flight?

b. On the downward part of the trajectory, when will the height of the stone be 10 m above the base of the trebuchet?