If $A$ and $B$ are events of a random experiment such that $P(A \cup B)=\large\frac{4}{5},$$ P(\bar {A} \cup \bar {B})=\large\frac{7}{10}$ and $P(B)=\large\frac{2}{5},$ then $P(A)=$

Question

\[\begin {array} {1 1} (1)\;\frac{9}{10} & \quad (2)\;\frac{8}{10} \\ (3)\;\frac{7}{10} & \quad (4)\;\frac{3}{5} \end {array}\]