A bank offers 20% compound interest per half year. A customer deposits Rs 2800 each on 1st January and 1st July of a year. At the end of the year, the amount he would have gained by way of interest is ______.
If the time increases by 5 years, then simple interest increases by Rs 3000 on a sum of Rs 5000. What is the rate (in percentage) of interest per annum?