def average_change(profit_loss):
    """
    Function returns average change of the numbers in the list using formula (last_element - first_element)/(number of elements - 1)
    """
    
    profit_loss_copy = profit_loss[:]
    average_ch = (profit_loss_copy[-1] - profit_loss_copy[0])/(len(profit_loss_copy)-1)
    return round(average_ch, 2)