Sounds like a weird exam to me. I don't know what it would prove except the ability to hurry or mass produce. A better exam would be to produce a portfolio of 6 prints over the course of the whole semester.
Even when I'm just cranking out 8x10 proof prints it can sometimes take me up to 45 min per to get it worked out, and that's about all the time they are giving you. As the others have said, when it comes to making good final prints it can take hours, days, even years.