Discrete structures let s(x, y) mean that x and y are siblings, p(x, y) mean that x is a parent ofy, c(x, y) mean that x and y are cousins, x = y mean that x and y are the same person and x +y mean that x and y are distinct people express each of the english sentences below in predicate logic. a) two people are siblings if and only if they are distinct and have a parent in common. (that means for any x and y, x and y are siblings if and only if they are distinct and there exists a third person, say z, such that z is the parent of x and z is the parent of y.) b) if two people are cousins then they have parents who are siblings. (that means if x and y are cousins, then there's a u and a v such that u is a parent of x, v is a parent ofy and u and vare siblings.) c) there exist three distinct people, say x, y and z, such that x is a cousin ofy and y is a cousin of z but x is not a cousin of z. (note that x+y+z isn't the same as saying x and y and z are all distinct because it allows x and z to be equal. to express that three people are distinct you need three inequalities.)