Solve the Problem $68.6 \mathrm {~m}$ High as It Is Falling, Its Height Is Given by Is

Solve the problem.
-A rock falls from a tower that is $68.6 \mathrm {~m}$ high. As it is falling, its height is given by the formula $h = 68.6 - 4.9 t ^ { 2 }$ , with $t$ in seconds. How many seconds will it take for the rock to hit the ground (h $= 0$ ) ?

A) $960.4 \mathrm { sec }$
B) $8 \mathrm { sec }$
C) $3.7 \mathrm { sec }$
D) $8.3 \mathrm { sec }$