Concurrent auditing for export related transaction thru bank

1) First of all i want to know all the types of Export transaction that takes place through Bank with short descripttion of each type.

2) Duty of concurrent Auditors in case of xport transactions.

3) I'm not able to understand Bills purchased and Negotiated by Bank. Pls someone explain its meaning with the help of a example

4) Also wht is meant by Fund based and Non fund based advance. Wht is Bank Gurantee and why it is regarded as one of the example of bank Gur'tee.

5) Pls share ur views or experience regarding export transaction while doing concurrent Auditing

i want to ask many question regarding this type of auditing.

Pls help...