I got some chickens from a friend several months back. The issue is my friend only knew they were egg layers. This chicken is about 5 or 6 months old and is a female.
White Rock. It lacks the white earlobe of a Leghorn. I would say Rhode Island White would be unlikely because they're uncommon and are "supposed" to have a rose comb as it's the only APA accepted variety, in contrast to the bird in the picture. Some hatcheries do sell a single comb variety though.