In the figure shown, blocks A, B and C weigh 3 kg, 4 kg and 8 kg respectively. The coefficient of sliding friction between any two surfaces is 0.25. A is held at rest by a massless rigid rod fixed to the wall while B and C are connected by a string passing round a frictionless pulley. Find the force needed (in N) to drag C along the horizontal surface to left at constant speed. Assume the arrangement shown in figure is maintained all through. Take g=10m/s2