Each of six teachers M, N, P, Q, S and I have their classes on six different days of a week starting from Monday and ending on Saturday of the same week, but not necessarily in the same order. Only two teachers have classes before N's class. 'S' has the class on Tuesday and 'O' has the class on Saturday. Only one teacher has the class after the class of 'M'.  P's class is not between the classes of 'M' and 'N'. Who among the following has the class on Monday?