mtimes

auto a =
    [-5,  1,  7, 7, -4,
     -1, -5,  6, 3, -3,
     -5, -2, -3, 6,  0]
        .sliced(3, 5)
        .universal
        .transposed;

auto b = slice!double(5);
b[] = [-5, 4,-4,-1, 9];

assert(mtimes(b, a) == [-42, -69, 23]);