PLEEEEEEASE HELP ME THIS IS VERY LATE WORK

Nine thousand, ten and two hundred thirty-one thousandths
9,000 + 10 + 0.02 + 0.003 + 0.0001
David made a mistake when writing the number above in expanded form.

Part A. Find Davids Mistake and correct it.

Part B. Explain why Davids expanded form of the number was wrong.