Give the step-by-step reasoning process and then the final answer. Alex has 4 new shirts. Joe has 3 more new shirts than Alex. If Ben has eight more new shirts than Joe, how many new shirts does Ben have?

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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Joe has 4 + 3 = 7 new shirts. Ben has 8 + 7 = 15 new shirts.
The final answer: 15.