$24.$ Channel Tunnel Inc. plans to build an additional $23-$mile$-$long tunnel under the English Channel for added train service. The cost $($NINV$)$ of the tunnel is expected to be $$2\mathrm{.}1$ billion. Net cash inflows are expected to equal $$364$ million per year. How many years must the firm generate this cash inflow stream for investors to earn their required $17$ percent rate of return? Use Table IV to answer the question. Round your answer to the nearest whole number.

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