How is Zakat calculated on a commercial establishment that started with a capital of 300,000 Riyals, achieved a profit of 100,000 Riyals, and had annual expenses of 70,000 Riyals?

Zakat is obligatory on the remaining money after deducting dues, if it reaches the نصاب (minimum threshold) and a whole year has passed over it. There is no difference in the obligation of Zakat on the remaining amount, whether it is profit or capital.