A prototrophic hfr strain is used to map four genes responsible for amino acid synthesis in an interrupted mating experiment (conjugation takes place during mating)

A prototrophic hfr strain is used to map four genes responsible for amino acid synthesis in an interrupted mating experiment (conjugation takes place during mating). The genotype for the Hfr strain is asp⁺ phe⁺ trp⁺ cys⁺ kan^s, and the genotype for the F^- strain is asp^- phe^- trp^- cys^- kan^r (Note that the allele listing does not imply the gene order, and cells with kan^r are resistant to the antibiotic kanamycin). Mating starts at 0 min, and the mating mixture is spread onto four plates at various times. A specific combination of amino acid supplements is added to each plate containing the minimal medium (MM) and kanamycin as indicated in the table. The table shows the number of colonies that grew on each plate at every time point. 
A. What is the purpose of kanamycin in this experiment?

B. What is the order of these genes? (Write the order from first to last).

C. What is the distance between phe and trp? 

D. In the recipient strain, ideally where should the kan^r gene map?