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Consider an aligned fiber reinforced$-$polymer matrix composite for which the constituent fibers have diameter and average fiber length values of $1\mathrm{.}5{10}^{-2}mm$ and $7\mathrm{.}5$ mm $,$ respectively. Given a fiber strength of $3500$ MPa and a fiber$-$matrix bond strength of $75$ MPa for this composite, which of the following equations should be used to determine the tensile strength in the direction of fiber alignment?

${}_{cd}^{**}={}_f^{**}{V}_f(1-\frac{l_c}{2l})+{}_m^{\text{'}}(1-V_f)$

${}_{cd}^{**}=\frac{l{}_c}{d}{V}_f+{}_m^{\text{'}}(1-V_f)$

${}_{cl}^{**}={}_f^{**}{V}_f+{}_m^{\text{'}}(1-V_f)(1-\frac{l_c}{2l})$