Sally wants to purchase a machine that produces beads to make jewelry. The machine produces 1000 beads every half hour. She can use 40 beads to make a necklace which sells for $5 or use 25 beads to make a bracelet that sells for $3. The machine costs $5000 and she uses it for 2.5 hours a day.
Assuming she wants to make 4 times as many necklaces as bracelets, after how many days will the machine pay for itself?
