Generalized transducing phage

With the use of P22 as generalized transduction phage grown on a pur+ pro+ his+ bacterial donor, a recipient strain of genotype pur – pro – his - is infected and incubated. Afterward, transductants for pur+, pro+, and his+ are selected individually in experiments I, II, and III, respectively.

a. What media are used for these selection experiments?



b. The transductants are examined for the presence of unselected donor markers, with the following results:

I                                 II                              III
pro – his - 87%           pur - his- 43%           pur – pro – 21%
pro+ his - 0%              pur + his- 0%           pur + pro – 15%
pro - his+ 10%          pur – his+ 55%           pur – pro + 60%
pro+ his+ 3%            pur + his + 2%            pur + pro + 4%

What is the order of the bacterial genes?

Ok, so this is what i have so far

a. I Minimal media plus proline and histidine
   II Minimal media plus purines and histidines
  III Minimal media plus purines and prolines

(Is this right)

Plz help me, ive been stuck on this one question for hours =/