Correct Answer - C
(3) `R_(1) = (L)/(K_(1). pi R^(2)), R_(2) = (L)/(K_(2) (4 pi ^(2) - pi R^(2))) = (L)/(3 k_(2) pi R^(2))`
`R_(eq) = (L)/(K_(eq). 4 pi R^(2))`
`R_(1)` and `R_(2)` are in parallel `(1)/(R_(eq)) = (1)/(R_(1)) + (1)/(R_(2))`
`(4 pi R^(2) K_(eq))/(L) = (pi R^(2) K_(1))/(L) + (3 pi R^(2) K_(2))/(L)`
`K_(eq) = (K_(1) + 3 K_(2))/(4)`