Rate of Interest is 5%
Principal (P) = 6000
Amount (A) = 6615
no. of years (n) = 2
Let 'r' be rate of interest.
Compound Interest formula:
A = P (1+r/100)^n
6615 = 6000(1+r/100)^2
6615/6000 = (1+r/100)^2
(6615/6000)^(1/2) = 1+r/100
1.05 = 1+r/100
r/100 = .05
r = 5%