def solve(self, A, F, N, b):
        """
        Solve linear system ``Ax = b`` using numeric factorization ``N`` and symbolic factorization ``F``.
        Store the solution in ``b``.

        Parameters
        ----------
        A
            Sparse matrix
        F
            Symbolic factorization
        N
            Numeric factorization
        b
            RHS of the equation

        Returns
        -------
        None
        """
        if self.sparselib == 'umfpack':
            umfpack.solve(A, N, b)

        elif self.sparselib == 'klu':
            klu.solve(A, F, N, b)