Dilution problem

by Noor
(Canada)

Hello,I'm having such a hard time setting up proportion math,
i just can't figure it out which number suppose to go on top and bottom,so please help me my friend?
Here is my question:

Rx cephazolin 2% ophthalmic drops 10 ml.

To make this order,use cephazolin injection 500 mg/10 ml vial.

How many milliliters from the vial of cephazolin will be in the final preparation?


thank you!