There has been a rumor going on that the pass marks is 28 out of 70. Those who claim that they had seen the notification in wbut.ac.in,
do not deserve to be engineers as their reading and understanding skills are negligible. Only they know how to spread rumors. Here's the link
http://www.wbut.ac.in/datas/users/0-notice.pdf
What is says is that a student have to pass(obtain a D grade) in each of theory(70+30internal),laboratory and sessional items like NSS, system design,seminars etc.
Regarding year lag here's the link
http://www.wbut.ac.in/datas/users/0-notice_1.pdf
For original/previous regulations
Herez the link
http://www.wbut.ac.in/datas/users/0-first_degree.pdf
