Christmas eve is near, and most of Santa's elves were on vacation
except for 4 elves. These 4 elves were helping Santa make toys for Christmas. The Blue
Elf can make 500 toys in one hour. The Red Elf can make 800 toys in two
hours. The Green Elf can make 300 toys in half an hour. The Yellow
Elf can make 750 toys in one hour. If there were still 12,000 toys left to
make for Christmas, in how many hours can these toys be completed by these 4
elves working together?