Verified Answer :

\(h = -4..9t^2+27t+2.4\ for\ t=3\)

Just replace t with 3 and solve.

\(h = -4.9*3^2 + 27*3 + 2.4 \\ h = -4.9*9 + 27*3 + 2.4 \\ h=-44.1 + 81 + 2.4 \\ \boxed{h=39.3}\)