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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 _compute_sigma_b(self, C, mag, vs30measured):
 """ Equation 23, page 81. """

        sigma_0 = self._compute_sigma_0(C, mag, vs30measured)
        sigma_amp = self.CONSTS['sigma_amp']

        return np.sqrt(sigma_0 ** 2 - sigma_amp ** 2)