Uitwerkingen 2c, 2d.

2c. (p or q) -> ( not r and not q) = not ( p or q) or ( not r and not q) = 
    (not p and not q) or (not r and not q) = 
    (not p or not r) and (not p or not q) and (not q or not r) and (not q or not q) =
    (not p or not r) and (not p or not q) and (not q or not r) and not q =
    (not p or not r) and not q

2d. (p or q or r), (not p or q), (not r or q), (t or not q) |=R 
    (q or r), (not r or q), (t or not q) |=R 
    q, (t or not q) |=R
    t