intro3.py

import numpy as np

earnings = [
            [
                [500,505,490],
                [810,450,678],
                [234,897,430],
                [560,1023,640]
            ],
            [
                [600,605,490],
                [345,900,1000],
                [780,730,710],
                [670,540,324]
            ]
          ]
          
earnings = np.array(earnings)

gt500 = earnings[earnings > 500]

mmean = np.mean(earnings[:,0,:])