M_{x} and M_{y} denote the atomic masses of the parent and the daughter nuclei respectively in a radioactive decay. The Q-value for a β ^{–} decay is Q_{1} and that for a β ^{+} decay is Q_{2}. If me denotes the mass of an electron, then which of the following statements is correct?

(a) Q_{1} = (M_{x} – M_{y}) c^{2} and Q_{2} = (M_{x} – M_{y} – 2m_{e})c^{2 }

(b) Q_{1} = (M_{x} – M_{y}) c^{2} and Q_{2} = (M_{x} – M_{y} )c^{2}

(c) Q_{1} = (M_{x} – M_{y} – 2m_{e}) c^{2} and Q_{2} = (M_{x} – M_{y} +2 m_{e})c^{2 }

(d) Q_{1} = (M_{x} – M_{y} + 2m_{e}) c^{2} and Q_{2 }= (M_{x} – M_{y} +2 m_{e})c^{2}