a b c d

c

$ \text { u = -f , F = +f }$ $ \frac{1}{f} = \frac{1}{v} + \frac{1}{u} $ $ \frac{1}{v} = \frac{1}{f} - \frac{1}{u} = \frac{1}{f} - \frac{1}{-f} = \frac{2}{f} $ $ v = \frac{f}{2} \text{ Behind the Mirror}$