A sales representative plans to visit each of six companies M, N, P, Q, R and S exactly once during the course of one day. She is setting up her schedule for the day according to the following conditions :
(i). She must visit M before N and R.
(ii). She must visit N before Q.
(iii). The third company she visits must be P.
Which of the following must be true of the sales representative's schedule ?
Clearly, she visits M before N and N before Q. So, she must visit M before Q.