Hello! I'm in Organic Chemistry Lab and I'm having a rough time with this problem:

Suppose you wish to extract 10 g of benzoic acid from an ether solution with aqueous NaHCO3.

What is the minimum amount of NaHCO3 that must be added to 50 mL of water to carry out the extraction?

So I'm assuming we use the extraction formula:

Mass_{StillInWater} = Mass_{initial}[(Vol_{water})/((K*Vol_{ether})+Vol_{water})]

Then I subtract Mass_{StillInWater} from Mass_{initial} to get 10g.

The question doesn't give us a K value or the volume of ether so I'm a little lost in how to begin with this question. I'm not even sure if I'm doing it right. Any help would be appreciated.