The minimum kinetic energy needed by an alpha particle to cause the nuclear reaction ${ }_7^{16} \mathrm{~N}+{ }_2^4 \mathrm{He} \rightarrow{ }_1^1 \mathrm{H}+{ }_8^{19} \mathrm{O}$ in a laboratory frame is n (in MeV ). Assume that ${ }_7^{16} \mathrm{~N}$ is at rest in the laboratory frame. The masses of ${ }_7^{16} \mathrm{~N}_{, 2}^4 \mathrm{He},_1^1 \mathrm{H}$ and ${ }_8^{19} \mathrm{O}$ can be taken to be $16.006 \mathrm{u}, 4.003 \mathrm{u}, 1.008 \mathrm{u}$ and 19.003 u , respectively, where $1 \mathrm{u}= 930 \mathrm{MeVc}^{-2}$. The value of $n$ is $\_\_\_\_$ .