Problem 6.269

An alpha particle with kinetic energy $T=5.3 \mathrm{MeV}$ initiates a nuclear reaction $\mathrm{Be}^{9}(\alpha, n) \mathrm{C}^{12}$ with energy yield $Q=$ $=+5.7 \mathrm{MeV}$. Find the kinetic energy of the neutron outgoing at right angles to the motion direction of the alpha-particle.