P$5\mathrm{.}41$ A certain axial$-$flow turbine has an output torque $\backslash ($ M $\backslash )$ which is proportional to the volume flow rate $\backslash ($ Q $\backslash )$ and also depends upon the density $\backslash (\backslash$rho $\backslash ),$ rotor diameter $\backslash ($ D $\backslash ),$ and rotation rate $\backslash (\backslash$Omega $\backslash ).$ How does the torque change due to a doubling of $($a$)\backslash ($ D $\backslash )$ and $($b$)\backslash (\backslash$Omega $\backslash )?$