What is the method for calculating the Zakat on five thousand Egyptian pounds deposited in a bank and five thousand Egyptian pounds invested in a project, and is there a specific amount that wealth must reach for Zakat to be obligatory upon it?

The amount of paper currency or trade goods on which zakat (definition) is due is that which is equivalent to 85 grams of gold. This is the minimum threshold (nisab (definition)) at which wealth becomes liable for zakat, because the nisab for currencies follows that of gold. The nisab for gold is twenty dinars, which weighs approximately 85 grams. It is not permissible to deposit money in usurious banks except out of necessity. Of what is deposited therein, only the principal amount is subject to zakat; the usurious interest is not subject to zakat. Rather, one must dispose of it by spending it on charitable causes.