# I need to prove the validity of these problems by using the 18 proof rules.

**Question description**

(1) 1. ~M or N

2. ~R implies ~N/: M implies R

(2) 1. ~A implies (B and C)

2. ~C/: A

(3) 1. H implies K

2. C iff D

3. ~C implies ~K/: H implies D

(4) 1. (A and B) implies C

2. A and ~C/: ~B

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