Excuse me but no one here is going to solve anything for you. This is a help forum where we help students solve their problems. What helpers here never do is solve a problem for a student-that is your job!
Here is a hint: Divide 51000 by 4 (using long division or any other division method you know) and see what the remainder is?
Do you know what a remainder is??
If you go into a store with $51,000 and keep buying an item that cost exactly $4 each (no tax), how much money will be left in the end? That will be your remainder.