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Nilanjan Bhowmick AIR 3, CSIR NET (Earth Science)
Deepak singh 1
Refer attachment
But the answer was given 9π.
I have find surface integral , bcoz there was no vector sign on dS in your post /question . If there is vector sign or any information of vector given in question then we put dS= n^ds .
if its flux then your solution may be correct .
if have doubt then ask ..