  The life-time of the four-body atomic system MuPs ($\mu^{+} e^{-}_2 e^{+}$ or
muonium-positronium) against positron annihilation has been evaluated as $\tau
= \frac{1}{\Gamma} \approx 4.076453 \cdot 10^{-10}$ $sec$. Various annihilation
rates for MuPs are determined to a good numerical accuracy, e.g., $\Gamma_{2
\gamma} \approx$ 2.446485$\cdot 10^{9}$ $sec^{-1}$, $\Gamma_{3 \gamma} \approx$
6.62798$\cdot 10^{6}$ $sec^{-1}$, $\Gamma_{4 \gamma} \approx$ 3.61680$\cdot
10^{3}$ $sec^{-1}$, $\Gamma_{5 \gamma} \approx$ 6.32973 $sec^{-1}$. The
hyperfine structure splitting for the ground state in the MuPs system has also
been evaluated as $\Delta$ = 23.078 $MHz$.
