Pks guide me, thank you....

A source emits spherical waves with equal intensity in all directions. The intensity of the wave 42.5 m from the source is 197 mW/m2. Compute the power output of the source.

imagine the sourse enclosed in an sphere of radius 42.5 m. The energy passing through unit area per unit time or the power per unit area is given by 197 unit( pls use the actual unit) as this is the definition of intensity. Now the total power will be = intesity*area of the sphere = (197E-6)*4II*42.5^2 W