Three particles $P, Q$ and $R$ are moving along the vectors $\overrightarrow{A}=\hat{\mathrm{i}}+\hat{\mathrm{j}}, \overrightarrow{\mathrm{B}}=\hat{\mathrm{j}}+\hat{\mathrm{k}}$ and $\overrightarrow{C}=-\hat{\mathrm{i}}+\hat{\mathrm{j}}$, respectively. They strike on a point and start to move in different directions. Now particle $P$ is moving normal to the plane which contains vector $\overrightarrow{A}$ and $\overrightarrow{B}.$ Similarly particle $Q$ is moving normal to the plane which contains vector $\overrightarrow{A}$ and $\overrightarrow{C}.$ The angle between the direction of motion of $P$ and $Q$ is ${\cos }^{-1}\left(\frac{1}{\sqrt{x}}\right).$ Then the value of $x$ is $\underline{ }$ $.$

Hence, the correct answer is 3.