A stone is tossed from a point W into the air. The height Y metres of the stone above ground level at time t seconds is given by y=-t2+4t+5.
(a) How far is W from the ground level?
(b) If -t2+4t+5 can be expressed as -(t-2)2 +P, find the value of P.
(c) Hence, deduce the maximum vertical distance of the stone above the point W and the time taken to reach thi distance.