The answer is B (The second one). I'm not sure though.
Assuming that reaching a height 0 doesn’t stop the ball, and that it accelerates at 9.8 m/s^2, the ball would be traveling at 0.5 + 0.7*9.8 = 7.36 m/s downwards.
Power = 
Delilah: 170J/30s = 5.66 W
Adam: 260J/20s = 13 W
I try to aim a the right key or do typing lessons