Two coils $\mathrm{P}$and $\mathrm{Q}$ are kept near each other. When no current flows through coil $\mathrm{P}$ and current increases in coil$\mathrm{Q}$ at the rate $10 \mathrm{A} {\mathrm{s}}^{-1}$, the e.m.f. in coil $\mathrm{P}$ is $15 \mathrm{mV}$. When coil $\mathrm{Q}$carries no current and current of $1.8 \mathrm{A}$ flows through coil $\mathrm{P}$, the magnetic flux linked with the coil $\mathrm{Q}$ is