Santa rides his bike over a piece of gum and continues riding at a constant rate. At time = 1.25 seconds, the gum is at its maximum height off the ground. and 1 second later, it is on the ground again.

a. If the diameter of the wheel is 68 cm, write an equation that models the height of the gum in centimeters above the ground at any time, t, in seconds

b. What is the height of the gum when Santa reaches his workshop at the end of the block at 15.6 seconds?

c. When is the first and second time the gum reaches a height of 12 cm?