100 people are randomly positioned in a circle. 10 of the people are sick and not wearing masks. Of the other 90 people, 50 are wearing a mask and 40 are not. We say a person is isolated if the person to their left and right is wearing a mask.

a) What is the expected number of sick people who are not isolated?

b) For person i, let X_i be the indicator random variable of whether that person is isolated. If person i and j are not adjacent, is X_i independent from X_j?