Four students Akash, Bikram, Ramesh and Dewan joined a college in 1991, 1992, 1993 and 1994 but not necessarily in that order. Each student joined one of the four departments, viz. Physics, Chemistry, Mathematics and Biology. No two students joined the same department. One of those who joined the college before 1993 joined Chemistry. No one joined the college after Ramesh. Dewan joined Physics. Akash joined one year after Dewan but didn’t join Chemistry. The student who joined in 1992, joined the department of