ABC Corp. wants to emamine the ability of certain factors to explain or predict the number of units sold of its product(Y) over the past guarter by its sales force. Its market research department extracts a random sample of n=35 salesmen from its records and identifies the following m=4 variables as possible regressors or predictors: number of "cold" calls (visits) made (X1); number of follow-up calls (visits) made (X2); average amount of time (in minutes) spent with a client (X3); and the number of months of sales experience (X4). These observations appear in what follows, the aforementioned variables will be coded as such: units(Y); cold(X1); foll(X2); clt(X3); and exp(X4); Exhibit 12.1 contains the SAS code for generating the regression results