Is zakat obligatory on a saved amount of EGP 20,0, knowing that it is designated for purchasing a plot of land for building, and that EGP 43,0 was borrowed from the mother to cover the total price of the land? And what is the amount of zakat, if obligatory?

You are not obligated to pay Zakat on money that left your possession before the completion of the hawl (a full lunar year), nor on a plot of land that you do not intend for trade, based on the Prophet's (peace be upon him) saying: "There is no sadaqah (Zakat) on a man concerning his slave or his horse."