uestion 4 Let's suppose that we are interested in writing soine orma propositions about a bunch o people, some of whom are students in a school (called the U) and a bunch of courses, some of which are offered by the U . C(s): s is an offered course at the U S(x): is a student (at the U) E(r, s): student a is enrolled in course s F(x,y): a is a friend ofy For example, to write that there is an enrolled student who has a friend that is not a student, we could express that as Translate assertions (a) - (d) using only the predicates above, plus logical connectives, quantifiers, and equaliry between courses and between students, respectively). (a) Every student at the U is enrolled in at least one course at the U. (b) There is a course at the U that all students are enrolled in. c) Student r is enrolled in exactly 2 courses at the U x should be a free variable in your answerl. (d) When two students are friends, then they are enrolled in at least one course at the U in common