Simrat and Bir are partners in a firm sharing profits and losses in the ratio of 3 : 2. On 31st March, 2019 after closing the books of account, their Capital Accounts stood at Rs. 4,80,000 and Rs. 6,00,000 respectively. On 1st May, 2018, Simrat introduced an additional capital of Rs. 1,20,000 and Bir withdrew Rs. 60,000 from his capital. On 1st October, 2018, Simrat withdrew Rs. 2,40,000 from her capital and Bir introduced Rs. 3,00,000. Interest on capital is allowed at 6% p.a. Subsequently, it was noticed that interest on capital @ 6% p.a. had been omitted. Profit for the year ended 31st March, 2019 amounted to Rs. 2,40,000 and the partners' drawings had been: Simrat – Rs. 1,20,000 and Bir – Rs. 60,000. Compute the interest on capital if the capitals are (a) fixed, and (b) fluctuating.