@Chap X and Decent Baloch,
I have been a student of Accountancy for almost 6 years (With two gold medals). Moreover, I have almost 6 years of teaching experience of the same subject. But still I think it shouldn't be taken as optional subject because of uncertainty between American Accounting and British Accounting Systems. Furthermore, I requires in-depth study of many areas of accounting+taxation+I to B + Auditing +Types of accounting e.g cost, financial and advanced accounting etc.

Finally, its objective part of 40 marks is a kind of unusual one.

In my opinion, reconsider your options again.

However, Mercantile law is a kind of scoring subject and quite easy to prepare as well.