If dimensions of critical velocity, $v_{\mathrm{c}}$ of a liquid flowing through a tube are expressed as $\left[{\mathrm{\eta }}^{\mathrm{x}}{\mathrm{\rho }}^{\mathrm{y}}{r}^{\mathrm{z}}\right]$, where, $\mathrm{\eta },\mathrm{ }\mathrm{\rho }$ and $r$ are the coefficient of viscosity of liquid, density of liquid and radius of the tube, respectively, then, the values of $x$, $y$ and $\text{z}$ are given by