def time_per_line(
    desired_wpm, 
    words_per_line
):
    """
    Args:
        desired_wpm (int): the target words-per-minute value
                           you wish to achieve
        words_per_line (int): how many words per line your
                              test book contains on average
    Returns:
        seconds
    """
    # words_per_line * 1 min / 3 * desired_wpm
    minute_fraction = words_per_line/(3 * desired_wpm)
    return minute_fraction * 60