In the given figure the blocks $\mathrm{A}, \mathrm{B}$ and $C$ weigh $4 \mathrm{~kg}, 6 \mathrm{~kg}$ and 8 kg respectively. The co-efficient of sliding friction between any two surfaces is 0.5 . The force $\vec{F}$ required to slide the block $C$ with constant speed is $\_\_\_\_$ $\mathrm{N}_{\text {. (Use }} g=10 \mathrm{~m} / \mathrm{s}^2$ )