Answer
$$37.7 \mathrm{\ MeV} $$
Work Step by Step
$\text { From Eq. } 37-50 \text { , } $
$\begin{aligned} Q &=-\Delta m c^{2}=\left(m_{\Lambda^{0}}-m_{p}-m_{\pi^{-}}\right) c^{2} \\ &=1115.6 \mathrm{MeV}-938.3 \mathrm{MeV}-139.6 \mathrm{MeV}=37.7 \mathrm{\ MeV} \end{aligned} $
