Fluorescence quantum yield and fluorescence lifetime of a molecule are 0.4 and $5 \times 10^{-9}$ s, respectively. If the fluorescence decay rate constant is $Y \times 10^{7}\ \mathrm{s^{-1}}$, the value of Y (rounded off to nearest integer) is ________ 6. The number of photons emitted per nanosecond by a deuterium lamp (400 nm) having a power of 1 microwatt (rounded off to the nearest integer) is ________.