Use the formula R subscript t minus R subscript f t end subscript space equals alpha subscript i space plus beta subscript i left square bracket R subscript M t end subscript minus R subscript f t end subscript right square bracket plus epsilon subscript t to estimate the value of beta using a regression. Here R subscript t is the return on the stock and R subscript f t end subscript is the risk-free rate for the same period. R subscript M t end subscript is the return on a stock market index (in this case the S&P 500 index). alpha subscript i is the regression intercept, and beta subscript i is the slope (and the stock's estimated beta). epsilon subscript t represents the residuals for the regression. The intercept, alpha subscript i, is often called simply "the alpha". What does it measure