The hundreds digit is the 3.
Change every digit after the 3 to a 0.
Now you have 8,300.
Now look at the digit that was originally just to the right of the 3. It is a 5. Since 5 is from 5 to 9, the digit to its left goes up by 1. The 3 becomes a 4, and the answer is 8,400.
Answer: D: 8,400
