(a) says: Mrs. Anderson flies to Sweden tomorrow her plane leaves at 2:00 P.M.
This can't be right, because it's a run-on sentence! If someone were to say this outloud, it would sound as if someone wasn't "taking their time"!
(b) says: Mrs. Anderson flies to Sweden tomorrow, her plane leaves at 2:00 P.M.
This one looks correct. It has a comma which adds a pause. It also connects both statements made in the sentence.
(c) says: Mrs. Anderson flies to sweden tomorrow, and her plane leaves at 2:00 P.M.
This one wouldn't be correct because its listing ideas with "and" in between. It's as if the speaker is saying "she does this and this and that and that..."
