A periscope consists of two flat mirrors and is used for viewing objects when an obstacle impedes direct viewing. Suppose Curious George is looking through a periscope, in which the two flat mirrors are separated by a distance $L=0.400 \mathrm{~m}$, at the Man in the Yellow Hat, whose hat is at $d_{\mathrm{o}}=3.00 \mathrm{~m}$ from the upper mirror. What is the distance $D$ of the final image of the yellow hat from the lower mirror?