2d. [2 marks] David has two pairs of unbiased four-sided dice, a yellow pair and a red pair. Both yellow dice have faces labelled 1, 2, 3 and 4. Let S represent the sum obtained by rolling the two yellow dice. The probability distribution for S is shown below. S P(S=s) 2 = 1/16 3 = 2/16 4 = 3/16 5 = 4/16 6 = 3/16 7 = 2/16 8 = 1/16 The first red die has faces labelled 1, 2, 2 and 3. The second red die has faces labelled 1, a, a and b, where a < b and a, b e Zt. The probability distribution for the sum obtained by rolling the red pair is the same as the distribution for the sum obtained by rolling the yellow pair. Determine the value of b.​