The correct choice is (c) 44.1
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 * 0.9 * 10^3 N / m^3; y = 2.5m, A = ^1 ⁄ 2 * 2^2 = 2 m^2. Hence, F = 44.1 kN.