The geometric average annual return for a large capitalization stock portfolio is $10\%$ for ten years and $5\%$ per year for the next five years. The geometric average annual return for the entire $15$ year period is

A$.7\mathrm{.}89\%$

B$.8\mathrm{.}3\%$

C$.8\mathrm{.}72\%$

D$.9\mathrm{.}13\%$