When a certain biased die is rolled, a particular face occurs with probability 1/6 - x and its opposite face occurs with probability 1/6 + x. All other faces occur with probability 1/6.Note that opposite faces sum to 7 in any die. If 0 < x < 1/6,and the probability of obtaining total sum = 7,when such a die is rolled twice, is 13/96 , then the value of x is :
(1) 1/16
(2) 1/8
(3) 1/9
(4) 1/12
