profit and loss

        A man finds that it costs $ (300+4N) per day to make N articles. If the selling price of each article is $7, what are the minimum articles to be produced per day if he has to make a profit?

Answer:

SP of N articles = 7N

Profit: 7N – (300 + 4N)

For min. Profit 7N – (300 + 4N) > 0

Or, 3N > 300

Or, N > 100