A bank develops the following linear discriminant model of the credit quality (le., a higher Z means a better credit quality) based on their own loan database: 2 = 61X1 + B2X2 + B3X3 where X1 is volatility of sales revenue, X2 is return on asset (net income/total assets), and X3 is equity to debt ratio (equity value/long-term debts). Which statement below about the coefficients of three variables is correct? Select one: a. B1 is positive; B2 is negative; B3 is positive b. B1 is negative B2 is positive; B3 is positive c. B1 is positive; B2 is positive; B3 is negative d. B1 is positive: B2 is positive: B3 is positive e. B1 is negative; B2 is negative; B3 is negative X