Suppose a US investor has $$1950$ to invest and can choose either a US investment paying $4\mathrm{.}9\%$ or a foreign investment paying Rf$\%,$ where e is currently $11\mathrm{.}7$ and future e in one year is $13\mathrm{.}2.$ What value of Rf would leave the investor indifferent between investing at home or abroad?