Write a function ff that determines the rock's height above the road (in feet) in terms of the number of seconds tt since the rock was thrown.

$f(t)=f(t)=$

Hint: the function ff can be written in the form $f(t)=c\cdot (t-{t}_{1})(t-{t}_{2})\text{}f(t)=c\cdot (t-{t}_{1})(t-{t}_{2})$ for fixed numbers cc, t1t1,