Question 140091
not sure about a formula __ this is like a thought experiment


she needs a pair of each color, so what is the BEST case?
__ she picks 3 pairs, one of each color


but with no lights, she has to pick enough to be SURE she has one of each color
__ so what's the WORST case?
__ she picks 5 pairs, all white
__ then she picks 3 more pairs, all red
__ finally, she picks a black pair


so, to be SURE, she has to pick 9 pairs