A and B are two students.Their chances of solving a problem correctly are $\Large\frac{1}{3}$ and $\Large\frac{1}{4}$,respectively.If the probability of their making a common error is ,$\Large\frac{1}{20}$ and they obtain the same answer,then the probability of their answer to be correct is

Question

$\begin{array}{1 1} (A)\;\frac{1}{12}\quad(B)\;\frac{1}{40}\quad (C)\;\frac{13}{20}\quad(D)\;\;\frac{10}{13}\end{array} $