total time for a rock drop from top of the well to the bottom and the sound bouve back is 5.6 sec, the well dept is 450 ft, true or false

The time to fall would be sqrt(2H/g)= 5.3 s (using g = 32 ft/s62) . The time for sound to get be heard is 450 ft/(speed of sound) = 0.4 s

I get a total time to hear the sound to be 5.7 s.

I am not sure if they would consider that good agreement (with 5.6 s) or not. Your call.