Suresh lent out a sum of money to Rakesh for 5 years at simple interest. At the end of 5 years, Rakesh paid 9/8 of the sum to suresh to clear out the amount. Find the rate of simple interest per annum.

• A. 3.5% p. a.
• B. 2.5% p. a.
• C. 3% p. a.
• D. 2% p. a.