From the text do:

Exercise 2.4.1, p. 26. 

    1b to 1f

For those of you who do not yet have the text the questions are the following. This is a service that will not continue past the 3rd week.

Exercise 2.4.1, p. 26:

1.       Test the following formulas for S5-Validity. 

          Where necessary, unabbreviate the defined operators. 

          If any formula is not S5-Valid, provide a counter-example with a test to show that it is such

b.        []<>p É <>[]p 

c.        []([]p É []q) v []([]q É []p)

d.        (p É <>q) É (<>q É ~p)           (skeptic's thesis)

e.        (p É q) É ~<>(p & ~q)

f.         (~<>p É [](p É q))                     (a paradox of strict implication)