Please check my logic...

Mod Inc.'s beginning of October supplies was $400. Mod purchased $800 worth of supplies during October. At the end of October Mod's balance of supplies was $500. What will be Mod's end of October adjusting entry for supplies?

400+800-500=700

1. Debit supplies expenses for $900; Credit supplies for $900
2. Debit supplies for 700; credit supplies expenses for $700
3. Debit supplies expenses for $700; Credit supplies for $700
4. Debit supplies for $900; Credit supplies expenses for $900