Lets start with the equation to find force. Force is equal to the mass times the acceleration. Since the velocity is constant, the acceleration is equal to 0 so we have this equation.

F = m * a

F = (75kg) * (0 m/s^s) = 0

So the force exerted by the person is 0 N

So let's move to work. Work is equal to force times the displacement.

W = F * d

We use the force that we got in the first problem and displacement is given.