Multiple crosses were made between true-breeding lines of black and yellow Labrador retrievers. All the F₁ progeny were black. When these progeny were inter crossed, they produced an F₂ consisting of 91 black, 39 yellow, and 30 chocolate. 

(a) Propose an explanation for the inheritance of coat color in Labrador retrievers. 

(b) Propose a biochemical pathway for coat color determination and indicate how the relevant genes control coat coloration.