An analyst gathered the following data about a company:
　　Capital structure　　　Required rate of return
　　30% debt　　　　　　　　10% for debt
　　20% preferred stock　　　　11% for preferred stock
　　50% common stock　　　　18% for common stock
Assuming a 40% tax rate, what after-tax rate of return must the company earn on its investments?

A.13.0%.

B.14.2%.

C.18.0%.