How is the joint commercial wealth between two partners zakat-eligible, and is the gold saved at home zakat-eligible, and is it added to the commercial wealth?

For zakat to be obligatory on jointly owned wealth, the share of each partner must reach the nisab (equivalent to 85 grams of gold) and a hawl (full lunar year) must pass over it. Each partner pays zakat on his share when the hawl is due. If the wealth is derived from the growth of original capital (such as trade profit), it is added to the original capital, and its zakat is calculated along with the hawl of the original capital. However, if the gold is not a product of trade capital (such as a gift or inheritance), then if the partner's share in the jointly owned wealth reaches the nisab, he has the option to treat the gold as a new acquisition and pay its zakat when its hawl is due, or he may add it to the trade capital and pay its zakat along with it when its hawl is due. If his share does not reach the nisab except with the gold, then the hawl for zakat begins from the day the gold was acquired. Zakat is obligatory at a rate of a quarter of a tenth (2.5%).