Let's say that Jupiter, Neptune and Mars all have their own currencies. Here are the exchange rates: $2\frac{J}{N},1\mathrm{.}5\frac{N}{M},$ and $0\mathrm{.}4\frac{M}{J}.$ Given the other two rates, what should the exchange rate be between Mars and Jupiter?

a$.0\mathrm{.}333\frac{M}{J}$

b$.0\mathrm{.}40\frac{M}{J}$

c$.0\mathrm{.}667\frac{M}{J}$

d$.0\mathrm{.}75\frac{M}{J}$

e$.1\mathrm{.}333\frac{M}{J}$