Suggestions for a 30 minute WT routine?

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I’m looking for general suggestions on an effective, yet short, weight-training routine with the following restrictions:

1) Time limitation: 25-30 minutes for the gut of the workout. Total workout time: 35 minutes but I couldn’t imagine doing no stretching or warmup.
2) Number of days a week: 3-4
3) Equipment limitations: Small gym with variety of weight machines/a rack/free weights/barbells but not a lot of room and just one of everything. Thus, there can be waits on equipment or a free bench/free area/rack. You also don’t want to use anything for longer than 10 min. to be courteous to other exercisers.

General goals: Minimize loss of muscle mass while losing an add’l 10 pounds. Of course, I would like to get stronger and lift heavier weights as I progress with the workouts.

Any ideas? Resources? What are your ideas to work around these time limitations?