If / Then help, please!

I was asked to do the following, and I cant quite figure it out.

If A1 = (name) then it equals 1, if B1 = (name) then its .5, if C1= (name) then it equals .33. In addition, if B1 = (name) then A1 = .5 or if C1 = (name) then A1 and B1 equal .33.

Essentially there are three columns of names, some with names others with blanks. Each row of three columns represents ownership of a purchase of a mug. So if two people need to pay for a mug, then A1 and B1 would have a name in it; buy C1 would be blank.

Looks like this below, and attached:

Rep Rep 2 Rep 3
AG
AG BC
AG CT