text: import numpy as np
  
  def xa_to_dia(xa):
      '''
      Convert an array of cross-sectional areas to diameters wih units
      '''
  
      diameter = np.sqrt(xa *4 / np.pi)
      return diameter
  
  a = np.array([[6.7,1.3, 0.6, 0.7],
                  [0.1, 5.5, 0.4, 2.4],
                  [1.1, 0.8, 4.5, 1.7],
                  [1.5, 1.5, 3.4, 7.5]])
  b = np.array([1.1, 2.3, 3.3, 3.9])
  