I'm going to show the question that I'm really confused and I need your help
Let I (x) be the statement "x has an Internet connection" and C (x,y) be the statement "x and y have chatted over the Internet" where the domain for the variables x and y consists of all students in your class. Use quantifiers to express each of these statements
a) Rachel has not chatted over the Internet with Chelsea.
b) Jan and Sharon have never chatted over the Internet.
c) There are two students in your class who have not chatted with each other over the Internet.
d) There are at least two students in your class who have not chatted with the same person in your class.
e) There are two students in the class who between them have chatted with everyone else in the class.
I thought the negation of C (x,y) is "x and y have not chatted over the Internet" so I concluded
a) should be $\lnot $ C (Rachel,Chelsea).
but I feel ambiguous about b).
Does it mean Jan and Sharon have never chatted each other or they both have never chatted anyone else?
I concluded c) should be $\exists$ x $\exists $ y $\lnot $ C (x,y) and I don't know how to approach d) and e).
As a result, I want to know my answers on a) and c) are right or not and need your help on b),d),e)