Help Decorate ... In The DarkDiscrete Mathematics Level 2
A week ago, I helped Brian get his Christmas tree out and decorate it. He's very picky, so only wants exactly 2 baubles of each colour on the tree. He keeps all of his baubles in a box, which contains 10 reds, 8 blues, 6 yellows, 4 greens and 2 purples. It's dark, so I can't see the colour of the baubles. How many baubles do I have to pick out of the box in order to definitely meet Brian's requirements?