A parallel plate capacitor is made of two dielectric blocks in series. One of the blocks has thickness `d_(1)` and dielectric constant `K_(1)` and the other has thickness `d_(2)` and dielectric constant `K_(2)` as shown in figure. This arrangement can be through as a dielectric slab of thickness `d (= d_(1) + d_(2))` and effective dielectric constant `K`. The `K` is.
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A. `(K_(1)d_(1) + K_(2)d_(2))/(d_(1) + d_(2))`
B. `(K_(1)d_(1) + K_(2)d_(2))/(K_(1) + K_(2))`
C. `(K_(1)K_(2)(d_(1) + d_(2)))/(K_(1)d_(1) + K_(2)d_(2))`
D. `(2K_(1)K_(2))/(K_(1) + K_(2))`
