A spherical mirror forms an inverted image whose height is three times the height of the object. The image appears on a screen placed along the principal axis. Which of the following relationships between the magnitudes of the image distance si and the object distance so must be true under the standard sign convention?
a) ∣si∣=∣so∣
b) ∣si∣=3∣so∣
c) ∣si∣=∣so∣/3
d) ∣si∣=2∣so∣