51) A purse contain  4 copper and 3 silver coins, and a second purse contain 6 copper and 2 silver coins A coin is taken out from any purse, the probability that its is copper coin is .
$$\begin{gathered} \left(a\right) 3/7 \\ \left(b\right) 4/7 \\ \left(c\right) 3/4 \\ \left(d\right) 37/56 \end{gathered}$$