Is Zakat obligatory on a sum of 100,000 Saudi Riyals saved from the father's money, and is it permissible to give it to the two daughters?

Zakat becomes obligatory on wealth when it reaches the nisab (threshold) and a full hawl (lunar year) has passed over it. The nisab for gold is 85 grams, and for silver, it is 595 grams. Zakat is disbursed at a rate of 2.5% of the wealth.

The nisab for paper currencies is determined by their value in relation to gold or silver.

The amount your father deposits into the account is considered a monthly salary, and there are specific methods for calculating its zakat.

It is not permissible to pay zakat to daughters if their maintenance is obligatory upon the muzakki (the one paying zakat), which appears to be the case here, given that there is no one else to provide for them besides you.