Derivations (SD)

Hey all,

Can anyone give me an answer to these five derivations? They are in my
book and the damn book only has the answers on a CD that ONLY comes
with a new book! Argh. Textbook rip off. My class is over, so I have no
one to ask. How sad :(

The first three are being derived from an empty set.

a. |- (A -> C) -> ((B -> C) -> ((A v B) -> C))
b. |- (A -> ~B) -> (B -> ~A)
c. |- ((A <-> B) & (B <-> C)) -> (A <-> C)

The ones above I'm confused how to do. How do you derive an empty set?
The last two are also from the book, but are typical; I think.

d. {A -> B, B -> C, ~C} |- ~A
e. {~A v B, A} |- B

Anyone who has an answer, please type it. I'm off to try a few myself.
Out of all of Logic derivations are what got me. The rules of SD can be
found here:

http://www.unc.edu/~theis/logic/SDrules.html

Thanks

.

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