The Banker’s discount on a sum of money for 18 months is Rs. 600 and the true discount on the same sum for 3 years is Rs. 750/-. The rate percentage is:

• 10%

• 20%

• 12%

• 12%

A single discount equivalent to a discount series 15% and 5% is

• 32%

• 20%

• 21%

• 21%