The circuit shown in the figure consists of a charged capacitor of capacity $3 \mu \mathrm{~F}$ and a charge of $30 \mu \mathrm{C}$. At time $t=0$, when the key is closed, the value of current flowing through the $5 \mathrm{M} \Omega$ resistor is ' x ' $\mu-\mathrm{A}$. The value of ' $x$ to the nearest integer is $\_\_\_\_$ .