Given two 12-cm-focal-length lenses, you attempt to make
a crude microscope using them.While holding these lenses
a distance 55 cm apart, you position your microscope so that its objective lens is distance from a small object. Assume your eye's near point $N =$ 25 cm. ($a$) For your microscope to function properly, what should $d_{\circ}$ be? ($b$) Assuming your eye is relaxed when using it, what magnification $M$ does your microscope achieve? ($c$) Since the length of your microscope is not much greater than the focal lengths of its lenses, the approximation $M\approx N \ell/f_ef_\circ$ is not valid. If you apply this approximation to your microscope, what % error do you make in your microscope's true magnification?