(a) A concave mirror forms an inverted image four times larger than the object. Find the focal length of the mirror, assuming the distance between object and image is 0.600 $\mathrm{m}$ . (b) A convex mirror forms a virtual image half the size of the object. Assuming the distance between image and object is $20.0 \mathrm{cm},$ determine the radius of curvature of the mirror.