An electron, moving along the $x$-axis with an initial energy of 100 eV , enters a region of magnetic field $\overrightarrow{\mathrm{B}}=\left(1.5 \times 10^{-3} \mathrm{~T}\right) \hat{\mathrm{k}}$ at S (See figure). The field extends between $\mathrm{x}=0$ and $\mathrm{x}=2 \mathrm{~cm}$. The electron is detected at the point Q on a screen placed 8 cm away from the point S . The distance d between P and Q (on the screen) is (electron's charge $=1.6 \times 10^{-19} \mathrm{C}$, mass of electron $=9.1 \times 10^{-31} \mathrm{~kg}$ )