In a microscope the objective is having focal length $\mathbf{f}_{\mathbf{0}} = \mathbf{20~cm}$ eyepiece is having focal length $\mathbf{f}_{\mathbf{e}} = \mathbf{4~cm}$. The tube length is $\mathbf{32~cm}$. Then magnification produced by this microscope for normal adjustment is $\underline{\quad}$.