1.42 because you subtract 10 from the price
Answer:
20 m
Step-by-step explanation:
We are given that
Initial horizontal speed ,
Time, t=2 s
Initial vertical velocity, 
We know that

Where 
Using the formula


The negative sign indicates that the displacement of stone is in downward direction.
Hence, the height of the cliff is closest to 20 m
So distance is 14.4 km=14400m
the speed of Amy is 14400/40=360m/min
Bill spend 40+20=60min to arrive at school so his spped is 14400/60=240m/min
the difference between speeds is 360-240=120m/min
Answer: Amy faster on 120m/min