500
(We know it is backwards, this would be too hard in jeopardy form. Just pretend it isn't Jeopardy for a few seconds. Now, back to the question:) Why do the posters in the front of Mrs. Machado's room say "Sra. Machado, me presta un lapiz por favor" and "me prestas un lapiz por favor"?
In the first one, you are asking Sra. Machado for a pencil, and you have call her Ud. so the ending is -a. In the second, you are asking a friend, so it is -as.