B be a for b months. Then, A's investment = 3a for 2b months A : B = (3a x 2b) : (a x b) = 6AB : AB = 6 : 1Let the total PROFIT = m.Then. m x 1/7 = 6000 m = 6000 x 7 = 42000 20% of 42000 = 8400