How is zakat calculated on money invested in goods and real estate after the remaining amount has fallen below the nisab?

Zakat becomes due based on the Hijri year. Once wealth reaches the nisab, a quarter of a tenth (2.5%) of its value is to be given after the completion of one year (hawl). Wealth acquired during the year is known as mal mustafad (benefited wealth), and it is more prudent to pay its zakat along with the rest of the wealth upon the completion of the hawl. The hawl for trade goods is the hawl of the money with which they were purchased. Upon the completion of the Hijri year, the value of the wealth and trade goods (such as merchandise and apartments prepared for trade) is calculated, and a quarter of a tenth (2.5%) of their total is to be given. As for existing land, if it will be sold along with a house after its construction, its value is assessed, and a quarter of a tenth of its value is to be given. If it will not be sold, zakat is not obligatory on it until the apartments are built and their value is assessed.