Is Zakat obligatory on an amount of thirty thousand Riyals deposited in the bank's safety deposit box, and how is it calculated with the constantly changing unit price?

Zakat is obligatory on this amount if a year has passed over it and it has reached the nisab (the value of 85 grams of gold or 595 grams of silver). The amount of zakat is 2.5%. It is not permissible to deposit money in an interest-based bank except in cases of extreme necessity, with the obligation to dispose of its interest by spending it on the welfare of Muslims.