One set of barrettes costs $3 each, and one comb costs $1 each. Kristine buys one set of barrettes and one comb. Crystal buys three sets of barrettes and one comb. How much do the two girls spend altogether? Let's think first. Chain of thought:

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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Kristine spends $3 + $1 = $4. Three sets of barrettes cost 3 x $3 = $9. Crystal spends $9 + $1 = $10. Therefore, the two girls spend $4 + $10 = $14.
Therefore, the answer is 14.