Right choice is (c) 157
The explanation: Total liquid pressure on the lamina = F = γyA, where γ = specific weight of the liquid, y = depth of centroid of the lamina from the free surface, A= area of the centroid. Now, γ = 9.81 * 10^3 N / m^3; y = 1 + 3 – 1 / 2 = 2m, each side of the lamina =
Hence, F = 156:96 kN.