An amount of Rs. 14000 was borrowed at a certain rate of simple interest for 1 year. After four months further Rs. 4500 was added to it and the rate of interest on the total principal was doubled against the previous rate. At the end of the year, Rs. 3520 was paid as interest, calculate the rate of interest.
1
12% p.a
2
13% p.a
3
11% p.a
4
10% p.a