What force is required to hold a 4.6 tonne concrete slab in water?

The buoyancy force of Archimedes and the force of gravity act on a concrete slab in water:
P = m * g – ρw * g * V, where m is the mass of the concrete slab (m = 4.6 t = 4600 kg), g is the acceleration of gravity (g = 10 m / s ^ 2), ρ is the density of water (ρw = 1000 kg / m ^ 3), V is the volume of the submerged part of the slab (V = m / ρb, where ρb is the concrete density, we take ρb = 2300 kg / m ^ 3).
P = m * g – ρw * g * V = m * g – ρw * g * m / ρb = 4600 * 10 – 1000 * 10 * 4600/2300 = 46000 – 20000 = 26000 N = 26 kN.
Answer: A force of 26 kN is required to hold the concrete slab.