What is the amount of zakat due from the son who invested his money in buying and raising calves and earned 400,0 dollars, which he spent on buying fodder, and the second son who bought a hotel and a factory and earned 500,0 dollars, which he spent on buying a piece of land, knowing that both their profits have been spent?

If the son buys calves for trade, Zakat (definition) is due on them at a rate of a quarter of one-tenth of their value when a year has passed, and any profit made from their sale is added to this. If the money is spent before Zakat is paid, the Zakat does not lapse and remains a debt on him. However, if the calves are bought for rearing and to benefit from their milk, then they are subject to Zakat for cattle.

If the son buys a hotel and a factory with the intention of benefiting from their revenue, and not for trading them, then no Zakat is due on their value. Rather, Zakat becomes obligatory on their revenue if it reaches the threshold (nisab (definition)) and a year has passed over it. If the revenue is spent before Zakat is paid, the Zakat does not lapse and remains a debt on him.