code: def area_top_orifice(self):
          
          # Calculate the center of the top row:
          z = self.hl - 0.5 * self.b_rows
          # Multiply the stout weir width by the height of one row.
          return self.stout_w_per_flow(z) * self.q * self.b_rows
docs: Estimate the orifice area corresponding to the top row of orifices.
          Another solution method is to use integration to solve this problem.
          Here we use the width of the stout weir in the center of the top row
          to estimate the area of the top orifice