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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def RV_3(self):
 """Instantaneous RV of star 3 with respect to system center-of-mass """

        return -self.orbpop_long.RV * (self.orbpop_long.M1 / (self.orbpop_long.M1 + self.orbpop_long.M2)) +\
            self.orbpop_short.RV_com2