On the Discount Phoneline, any domestic long-distance call starting between 9 A. M. and 5 P. M. costs 15 cents a minute, and any other domestic long-distance call costs 10 cents a minute. So any domestic long-distance call on the Discount Phoneline that does not cost 10 cents a minute costs 15 cents a minute.
The pattern of reasoning in which the argument 'If a university class involves extensive lab work, the class will be conducted in a laboratory; otherwise, it will be conducted in a normal classroom. Thus, if a university class involves extensive lab work, it will not be conducted in a normal classroom' is most similar to that in the argument above.