To determine the gene order.....

[APmicro]

A cross is made between two E.coli strains....Hfr-arg+bio+leu+.....and F-arg-bio-leu-.....interrupted mating studies revealed that arg enters the recipient last. so arg+ recombinants are selcted on a medium containing only bio n leu. these recombinants are tested for the presence of bio+ and leu+. the following no. of individuals are found for each genotype....

arg+ bio+ leu+ 320
arg+ bio+ leu- 8
arg+ bio- leu+ 0
arg+ bio- leu- 48

find the gene order....i need an explanation too about how to go about the problem.....