Guests at a conference ate a total of fifteen chicken samosas. Each guest who was neither a student nor a vegetarian ate exactly one chicken samosa. No chicken samosa was eaten by any guest who was a student, a vegetarian, or both. If half of the guests were vegetarians, how many guests attended the conference?
(1) The vegetarians attended the conference at a rate of 2 students to every 3 non-students, half the rate for non-vegetarians.
(2) 30% of the guests were vegetarian non-students.