Answer:
4400 Joules
73.33 Joules
25.9325 Joules
Step-by-step explanation:
P = Power = 800 W
t = Time = 22 s
F = Force
r = Radius of arm = 90 cm
Energy

As the efficiency is 25%

Energy used in the race is 4400 Joules
Half of the energy is used in the arm

So, per stroke of paddle

The energy expenditure per arm stroke is 73.33 Joules
Displacement will be the half of the perimeter of the circle

Work done

The average force of the hand on the water is 25.9325 Joules