A nucleus with mass number 200 initially at rest emits and $\;\alpha-\;$ particle . If Q value of reaction is 4.2MeV .Then kinetic energy of $\;\alpha-\;$ particle will be

Question

$(a)\;4.2 MeV\qquad(b)\;4.116 MeV\qquad(c)\;3.96 MeV\qquad(d)\;1.9 MeV$