Question: Tom decided to go on a trip. During this trip, he needs to cross a lake, which in one direction takes 4 hours. During this time, Tom needs an assistant to help him with the crossing. Hiring an assistant costs $10 per hour. How much would Tom have to pay for help with crossing the lake back and forth?
Answer with step-by-step thinking: Crossing the lake two times (back and forth) would take 4 * 2 = 8 hours. So Tom would need to pay an assistant 8 * 10 = $80.
So the answer is 80.


Question: Lily types 15 words a minute and takes a 2-minute break every 10 minutes. How long does it take for Lily to type 255 words?
Answer with step-by-step thinking: It would take Lily 255 words / 15 wpm = 17 minutes to type without taking a break. Since Lily takes a break after 10 minutes of typing she takes 17 minutes + 2 minutes = 19 minutes.
So the answer is 19.


Question: Lana aims to sell 20 muffins at the bake sale. She sells 12 muffins in the morning. She sells another 4 in the afternoon. How many more muffins does Lana need to sell to hit her goal?
Answer with step-by-step thinking:

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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Lana sold 12 muffins and has to sell 20 - 12 = 8 to hit her goal before the bake sale ends. When she sells another 4 in the afternoon Lana has 8 - 4 = 4 muffins left to sell to meet her target.
So the answer is 4.