A and B entered into partnership investing Rs. 16,000 and Rs. 12,000 respectively. After 3 months A withdrew Rs. 5,000 while B added Rs. 5,000 to his capital. After 3 more months C joined them with a capital of Rs. 21,000. At the end of the year if they gained Rs. 26,400, then B's share of profit exceeds A's share by