Exercises from 4.7: 18 parts 2 and 3, 20 part 2, 21

Exercises from 5.6: 27

2003 Paper 6 Question 12 
a and c, skipping b. 
I don't mind looking at type derivations if you want to do them.

2004 Paper 5 Question 11 

2005 Paper 5 Question 11 (Try to attempt this without notes)

Prove a substitution lemma for the language in the above paper.