Establish the validity of this argument by means of an unmixed indirect derivation.

~(P-->Q)-->Q

P-->Q

Attempt:

1. Show P --> Q

2. ~ (P -->Q) Assumption( Indirect Derivation)

3. ~ (P -->Q) --> Q

4. Q

Remark: I cannot find the contradiction, and am not sure whether line 4 can be used for Indirect Derivation.