If one sells on installment and a lunar year has passed, does he pay zakah on the full amount or only on what he has received?

Question:
Honorable Shaykh, may Allah grant you success. He says: I bought a car for thirty thousand riyals and sold it on installment for fifty thousand riyals. The monthly installment is one thousand five hundred riyals, and I have accumulated eighteen thousand riyals. Do I pay zakah on what I have on hand, or on the full amount for which I sold it?

Answer:
You pay zakah on what you have with you, and you pay zakah on the entire remaining debt. You total it up and pay the zakah for every year. Yes.