You never know what is there in the examiner's mind, but it is always that Paper 3 is the one in which you will find in Bad debts and provision for doubtful debts. Still don't be so sure about it the examiner might still put it in paper 2.
Not really hard, but if compared to the whole syllabus it might be the most difficult. Nothing is there in it really, you just have to know the format that's all and then it is always being repeated. It is quiet easy.