Let A be the set of all statement forms in the three variables p, q, and r, and let R be the relation defined on A as follows. For all Sand Tin A, SRT + S and T have the same truth table. (a) in order to prove R is an equivalence relation, which of the following must be shown? (Select all that apply.) R is reflexive Ris not reflexive R is symmetric R is not symmetric R is transitive R is not transitive (b) Prove that is an equivalence relation. Show that it satisfies all the properties you selected in part (a), and submit your proof as a free response. (Submit a file with a maximum size of 1 MB.) Choose File no file selected (c) What are the distinct equivalence classes of R? There are as many equivalence classes as there are distinct ---Select--- distinct equivalence classes. Each equivalence class consists of B. Thus, there are --Select