B category is called management category.
General fee is 1.85L/yr for students who got admission through merit.
Management fee is 3.50L/yr for students who can get admission in the same college same group without merit(just like back door) but it also has some criteria like your 10+2 marks for us(2013 batch) pcm(physics,chemistry,mathematics) overall should be above 70%.
This management category fee varies with srm branch like ktr has highest value where as vadapalani and ramapuram has less value. So before paying caution.