Marking Scheme for PS2 Part B #1,2

Question 1 [10]
full marks for any grammar that works
no marks taken off for ambiguity

Question 2a [10]
full marks for giving example of a string with 2 parse trees

Question 2b [20]
10 marks for each direction of the proof (breakdown below)
5 marks for stating each direction of proof
5 marks for proving each direction