Three links are hinged together to form a triangle $A B C$ as shown in the figure. At a certain instant, the point $A$ is moving towards the mid point of $B C$ with a velocity of $5 \mathrm{~m} / \mathrm{s}$ and $B$ is moving at a perpendicular direction to $A C$. The velocity of point $C$ is :
(a) $5 \mathrm{~m} / \mathrm{s}$
(b) $10.4 \mathrm{~m} / \mathrm{s}$
(c) $10.8 \mathrm{~m} / \mathrm{s}$
(d) $1.8 \mathrm{~m} / \mathrm{s}$