Ignore my comment, that information is unnecessary.
Assuming no friction between the skis and the water, the total work performed on the skier is due only to the pulling force (T, for tension). By Newton's second law, the net force exerted on the skier is
∑ F = T = ma
where m = 73.5 kg is the mass of the skier, and a is their acceleration.
Under constant acceleration, the skier is pulled a distance x such that
(12.2 m/s)² - (5.2 m/s)² = 2ax
and solving for x gives
x = (60.9 m²/s²) / a
Then the total work performed on the skier is
W = Tx
W = ma • (60.9 m²/s²) / a
W = (73.5 kg) (60.9 m²/s²)
W ≈ 4480 J
