Three circles of different diameter are tangent externally. The triangle formed by the line joining their centers has sides 16 cm, 20 cm, and 24 cm, respectively. Find the area of the smallest circle in square cm.

Three circles of different diameter are tangent externally. The triangle formed by the line joining their centers has sides 16 cm, 20 cm, and 24 cm, respectively. Find the area of the smallest circle in square cm.