Given,

Inclination tallness (l) = 4 cm

Perimeter of upper roundabout finish of the frustum = 18 cm

\[\therefore 2\pi r_1\text{ }=\text{ }18\]

Or on the other hand, $r_1$ = 9/π

Likewise, periphery of lower end of the frustum = 6 cm

\[\therefore 2\pi r_2\text{ }=\text{ }6\]

Or on the other hand\[,\text{ }r_2\text{ }=\text{ }6/\pi \]  

Presently, CSA of frustum \[=\text{ }\pi \left( r_1+r_2 \right)\text{ }\times \text{ }l\]

\[=\text{ }\pi \left( 9/\pi +6/\pi  \right)\text{ }\times \text{ }4\]

$=\text{ }12\times 4\text{ }=\text{ }48\text{ }cm^2$