Calculate the solid angle subtended by the periphery of an area $1{\mathrm{cm}}^2$ at a point situated symmetrically at a distance of $5\mathrm{cm}$ from the area.

The volume of a liquid flowing out per second from a pipe of length $l$ and radius $r$ is written by a student as $V=\frac{\pi }{8}\frac{P r^4}{\eta l}$ where $P$ is the pressure difference between two ends of pipe and $\eta$ is coefficient of viscosity of the liquid having dimensional formula ${\mathrm{ML}}^{-1}{\mathrm{T}}^{-1}$. 

Check whether the equation is dimensionally correct or not.

If velocity of light $c$ , Planck’s constant $h$ and gravitational constant $G$ are taken as fundamental quantities then express mass, length and time in terms of dimensions of these quantities.