Niobium forms a substitutional solid solution with vanadium. Compute the number of niobium atoms per cubic centimeter for a niobium$-$vanadium alloy that contains $26$ wt$\%$ Nb and $764$wt$\%$ V$.$ The densities of pure niobium and vanadium are $8\mathrm{.}57$ and $6\mathrm{.}10$ g$/$cm$^3,$ respectively..