In an experiment, researchers are studying two genes in mice that control fur color and eye color. The genes are located on the same chromosome, and the alleles for the genes are as follows:

Gene 1: Black fur (B) is dominant to brown fur (b)
Gene 2: Red eyes (R) are dominant to black eyes (r)

In the F1 generation of a cross between two pure-breeding parents (BBRR x bbrr), all the offspring had black fur and red eyes. The F1 mice were then crossed with bbrr mice to produce the F2 generation.

Out of 100 F2 mice, the researchers observed the following phenotypes:

Black fur, red eyes: 48
Black fur, black eyes: 16
Brown fur, red eyes: 20
Brown fur, black eyes: 16

What is the recombination frequency between the two genes?