well, depends what you find most tricky
CH1: Lots of content, but pretty easy to get the hang of
CH2: Short chapter, very easy.
CH3: Generally easy once you've practiced, however some of the exam questions are horrendous.
CH4: Lots of content, but simple once you've learnt it
CH5: Looks hard, but is actually quite simple.
CH6: A case of committing several methods to memory.