A histogram with unequal bin widths represents the distribution of ages in a community. The frequency density ($FD$) for each class interval is shown below:

• $0 \le x < 10$: Width $= 10$, $FD = 1.2$
• $10 \le x < 20$: Width $= 10$, $FD = 1.8$
• $20 \le x < 40$: Width $= 20$, $FD = 1.5$
• $40 \le x < 50$: Width $= 10$, $FD = 2.0$

Using linear interpolation, what is the estimated median age of the community?