if the unit digit is 2 or 4 or 6 -- C3,1 cases the highest digit has C3,1 cases the rest 3 digits have P3,3 cases if the unit digit is 0 -- 1 case the highest digit has C4,1 cases the rest 3 digits have P3,3 cases total = C3,1 * C3,1 * P3,3 + 1 * C4,1 * P3,3 = 78 |