Priya has a recipe for banana bread. She uses 15 cups of flour to make 6 loaves of banana bread. Andre will use the same recipe. He will make b loaves of banana bread using f cups of flour. Which of these equations represents the relationship between b and f?

A. b=2/9f
B. b=2/5f
C. b=5/2f
D. b=9/2f