A beam of rectangular cross-section, as shown in the figure, is made of two perfectly bonded layers of different materials and equal thickness. The Young's moduli of the two materials are $E_{1}$ and $E_{2}$, where $E_{1}=2 E_{2}$. The beam is subjected to pure bending. If $t=1 \mathrm{~mm}$, the distance of the neutral plane from the top surface of the beam is __________ $\text{(in mm, rounded off to two decimal places)}$.
