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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 dRV(self, dt, band='g'):
 """Returns dRV of star A, if A is brighter than B+C, or of star B if B+C is brighter """

        return (self.orbpop.dRV_1(dt)*self.A_brighter(band) +
                self.orbpop.dRV_2(dt)*self.BC_brighter(band))