Use the Following Information to Answer the Question

Use the following information to answer the question.
A plantlike organism on the planet Pandora can have three recessive genetic traits: bluish leaves, due to an allele (a) of gene A; a feathered stem, due to an allele (b) of gene B; and hollow roots due to an allele (c) of gene C. The three genes are linked and recombine.
A geneticist performed a testcross with an organism that had been found to be heterozygous for the three recessive traits, and she was able to identify progeny of the following phenotypic distribution (+ = wild type) :

If recombination frequency is equal to distance in map units, what is the approximate distance between genes A and B?

A) 3 map units
B) 6 map units
C) 15 map units
D) 30 map units