The correct option is A Rs. 3,125
Here, amount paid by Mr. Black on final call is Rs 50*5,000 i.e. Rs 2,50,000. As per Table F of Schedule I to the Companies Act, 2013, if rate of interest on callis in arrears in not mentioned in the AOA of the company, then it shall be levied at 10% p.a. So, interest on final call paid by Black will be 10% of Rs 2,50,000 i.e Rs 25,000. Mr Black paid the shares 1.5 months later than last date of payment. So, the interest paid will be (Rs 25,000/12)*1.5 i.e. Rs 3,125.