P(A):The probability of getting head is $\frac{5}{10}*\frac{1}{2}+\frac{5}{10}*\frac{4}{5}=\frac{13}{20}$
Probability that second coin is= first fair * second fair + first unfair * second fair=
P(B):Probability that second coin is fair= $\frac{1}{4}*\frac{4}{9}+\frac{2}{5}*\frac{5}{9}=\frac{1}{3}$
conditional probability = $\frac{P(B)}{P(A)}=\frac{\frac{1}{3}}{\frac{13}{20}}=\frac{20}{39}$
Option A