On the Initial Day of Class (I

Multiple Choice

On the initial day of class (i.e. N=0 ) , a professor counts 480 students as being present in her math class. On the 11^th day of class (i.e. N=10 ) the professor counts 140 students as being present in her math class. If the number of students decreases in a linear fashion, what is the common difference d ?

A) -6
B) -18
C) -34
D) -48
E) None of the above.