Answer
The buoyant force is $~~2500~N$
$tension+buoyant~force = weight$
Work Step by Step
In part (a), we found that the downward force on the cube due to pressure is $3.71\times 10^4~N$
In part (b), we found that the upward force on the cube due to pressure is $3.96\times 10^4~N$
The buoyant force is the difference between these two forces:
$F_b = 3.96\times 10^4~N-3.71\times 10^4~N$
$F_b = 2500~N$
The buoyant force is $~~2500~N$
Since the cube is in equilibrium, the magnitude of the upward forces is equal to the magnitude of the downward forces.
That is:
$tension+buoyant~force = weight$
