The question says the machine uses up m gallons of oil each hour on weekends.
This means that if the machine works for 24 hours each day, it implies that:

There are only two days on weekends i.e. Saturday and Sunday.
This means that if the amount of oil used in 1 day in the weekend is 24m, then we can say:
Saturday: oil used is 24m
Sunday: oil used is 24m
Total oil used during the weekend is:
B.) 2,4,8,16,32 is the geometric series as the common ratio is equal for each step
Answer:
25 necklaces
Step-by-step explanation:
each necklace brings $16 profit (20-4=16)
400÷ 16= 25
so, at 25 necklaces, there will be enough profit to break even after paying for the advertising.
Answer: 12.57
Step-by-step explanation: