Question 1006967
OK, let t=time that both machines finish the job 
Now we know that machine A and B working together makes 1500+2500=4000 clips per hour
Now machine A works alone for 5 hours(8am-1pm) before machine B starts, so Machine A makes 1500*5=7500 clips leaving 23,500-7500=16,000 clips yet to be made.
Working together, machine A and machine B can make 16,000 clips in 16,000/4000=4 hours:

Sooo t=1:00pm +4 hours=5:00pm

Hope this helps---ptaylor