code: def _compute_mean(self, C, mag, rjb):
          
          m1 = 6.4
          r1 = 50.
          h = 6.
          R = np.sqrt(rjb ** 2 + h ** 2)
          R1 = np.sqrt(r1 ** 2 + h ** 2)
          less_r1 = rjb < r1
          ge_r1 = rjb >= r1
  
          mean = (C['c1'] + C['c4'] * (mag - m1) * np.log(R) + C['c5'] * rjb +
                  C['c8'] * (8.5 - mag) ** 2)
  
          mean[less_r1] += C['c3'] * np.log(R[less_r1])
          mean[ge_r1] += (C['c3'] * np.log(R1) +
                          C['c6'] * (np.log(R[ge_r1]) - np.log(R1)))
  
          if mag < m1:
              mean += C['c2'] * (mag - m1)
          else:
              mean += C['c7'] * (mag - m1)
  
          return mean
docs: Compute mean value, see table 2.