I/I0 = 0.85
I0/I = 1/0.85
A1(for 1 cm) = log(I0/I) = log(1/0.85) = 0.0706
Since A = e cl amd e and c are constant then A2(for 3 cm) = 3.0X0.0706
= 0.2117 = log(I0/I2)
I0/I2 = antilog 0.2117 = 1.628
%T = (I2/I0)100 = 100/1.628 = 61.4%
Answer is B