Hello All! I need help with this problem...

If a rock is is dropped from a cliff into an ocean, it travels approximately $\displaystyle 16t^2$ feet in $\displaystyle t$ seconds. If the splash is heard 4 seconds later and the speed of sound is 1100 ft./second, approximate the height of the cliff.

I thought the answer would just be: 4400 ft. I got a feeling I'm missing something. Any help would be great!