7. Suppose an urn contains 90 balls, 30 of which are known to be red, and 60 which are known to be either yellow or black, but in an unknown proportion. Explain why it is irrational to prefer B1 to B2, and also prefer B4 to B3, where B1 = A ball is drawn an you receive $100 if ball is red, B2 = A ball is drawn an you receive $100 if ball is black, B3 = A ball is drawn an you receive $100 if ball is red or yellow, B4 = A ball is drawn an you receive $100 if ball is black or yellow