An ice skater spins at $2\mathrm{.}5re\frac{v}{s}$ when his arms are extended. He draws his arms in and spins at $6\mathrm{.}0re\frac{v}{s}.$ By what factor does his moment of inertia change in the process?

a$.2\mathrm{.}4$

b$.1\mathrm{.}0$

c$.0\mathrm{.}42$

d$.0\mathrm{.}12$