John Receives a Marginal Benefit of $80 from One Missile

John receives a marginal benefit of $80 from one missile (a public good) . Nick receives a marginal benefit of $50 from one missile. Christina receives a marginal benefit of $65 from one missile. John, Nick and Christina are the only people in the economy. What is the economy's marginal social benefit from one missile?

A) $65
B) $195
C) $50
D) $80