A point mass is subjected to two simultaneous sinusoidal displacement in x-direction,$x_1\left(t\right)=A\sin \omega tand{x}_2\left(t\right)=A\sin \left(\omega t+2\pi /3\right)$ . Adding a third sinusoidal displacement $x_3\left(t\right)=B\sin \left(\omega t+\varphi \right)$  brings the mass to a complete rest. The values of   $Band\varphi$are