Null hypothesis & standard deviation

I need help with this study question:

You contacted a random sample of 36 graduates of Western University and learned that their starting salaires were $28,000 last year.  You then contacted a random sample of 40 graduates from Eastern University and found that their average starting salary was $28,800.  In each case, the standard deviation of the sample was $1,000.  

A.  Discuss how you would test the null hypthesis that there is no difference between average salaires received by the graduates of the two schools,  and

B.   Discuss what assumptions are necessary for this test?