Answer:
The tension in the cable when the craft was being lowered to the seafloor is 4700 N.
Step-by-step explanation:
Given that,
When the craft was stationary, the tension in the cable was 6500 N.
When the craft was lowered or raised at a steady rate, the motion through the water added an 1800 N.
The drag force of 1800 N will act in the upward direction. As it was lowered or raised at a steady rate, so its acceleration is 0. As a result, net force is 0. So,
T + F = W
Here, T is tension
F = 1800 N
W = 6500 N
Tension becomes :

So, the tension in the cable when the craft was being lowered to the seafloor is 4700 N.