A stock's beta coefficient can be calculated using the following equation:

a. Write a user-defined function that can calculate the beta coefficient. The argu ments to the function should be the covariance between the stock and market returns, and the variance of the market's returns. For example, BETA(COVAR AS SINGLE, MARKETVAR AS SINGLE)

b. Rewrite your function so that it accepts ranges of returns and then calcu lates the beta directly from the returns. It should be defined as: BETA(STOCK RETURNS AS RANGE, MARKETRETURNS As RANGE). Your function should make use of Application.WorksheetFunction to calculate the covariance and variance (use Excel's CovAR.S and VAR.S functions). In the code, be sure to check to see if the number of stock returns is equal to the number of market returns. The function should return an error if the count of returns is not equal.