** 17) Calculate the simple interest on Rs. 5640 invested for 7 months at 6% per annum.**

(A) 197.40

(B) 198.50

(C) 199.60

(D) 200.70

** 18) A sum of money becomes double on simple interest in 20 years. It will quadruple at the same rate in**

(A) 40 years

(B) 50 years

(C) 60 years

(D) 80 years