Assume that stock market returns do follow a single$-$index structure. An investment fund

analyzes $125$ stocks in order to construct a mean$-$variance efficient portfolio constrained by $125$

investments. They will need to calculate $\_\_\_\_\_\_\_\_$ estimates of expected returns and $\_\_\_\_\_\_\_\_$

estimates of sensitivity coefficients to the macroeconomic factor.

A$)125$; $15,225$

B$)125$; $125$

C$)7,750$; $125$

D$)15,625$; $125$