Sodium-21 Will Emit Positrons Each Having an Energy of 4

Multiple Choice

Sodium-21 will emit positrons each having an energy of 4.0 *10¯¹³ J. What is this energy in MeV?

A) 4.0 *10¯⁷ MeV
B) 2.5 MeV
C) 40 MeV
D) 2.5 * 10⁶ MeV
E) None of these choices is correct.