[Question]In preparation for his mountain climbing, Arvin wants to run a total of 20 kilometers in a week. On the first day, he ran 2 kilometers. On each subsequent day, he increased his running distance by 1 kilometer over the previous day. If he runs for 5 days a week, how many kilometers did he run on the 5th day?
[Answer]On the second day, Arvin ran 2 + 1 = 3 kilometers. On the third day, he ran 3 + 1 = 4 kilometers. On the fourth day, he ran 4 + 1 = 5 kilometers. So on the fifth day, he ran 5 + 1 = 6 kilometers. The answer is 6.

[Question]Suraya picked 12 apples more than Caleb, and Caleb picked 5 apples less than Kayla. If Kayla picked 20 apples, how many more apples did Suraya pick than Kayla?
[Answer]Caleb picked 20 - 5 = 15 apples. Suraya picked 12 + 15 = 27 apples. Suraya picked 27 - 20 = 7 apples more than Kayla. The answer is 7.

[Question]Bill put his french fries in the oven after it finished heating. The recommended time was 5 minutes for them to be fully cooked. He put them in for 45 seconds. How many seconds remained?
[Answer]Each minute last 60 seconds, so that means for the fries to be fully cooked Bill needs to cook them for 5 * 60 = 300 seconds. Since Bill had the fries in the oven for 45 seconds so far, that means they need to stay in the oven for another 300 - 45 = 255 seconds. The answer is 255.

[Question]Krista started raising chickens. She has 10 hens who lay eggs. She sells the eggs for $3 a dozen. In four weeks, she sold $120 worth of eggs. If she sold all the eggs her hens laid, how many eggs does each hen lay a week?
[Answer]

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
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At $3 a dozen, Krista sold $120 / $3 = 40 dozen eggs. If 10 hens laid 40 dozen eggs in 4 weeks, that means 40 dozen eggs / 10 hens = 4 dozen eggs were laid by each hen in four weeks. To find out how many eggs each hen laid in a week, 4 dozen eggs / 4 weeks = 1 dozen eggs each week. Since a dozen has 12 eggs, each hen lays 12 * 1 = 12 eggs each week. The answer is 12.