Assume that stock market returns do follow a single-index structure. An investment fund analyzes 500 stocks in order to construct a mean-variance efficient portfolio constrained by 500 investments. They will need to calculate ________ estimates of firm-specific variances and ________ estimate/estimates for the variance of the macroeconomic factor.

Select one:

a. 500; 1

b. 500; 500

c. 124,750; 1

d. 124,750; 500

e. 250,000; 500