Polarized Sunglasses

Polarized sunglasses first became available in 1936, which use the phenomenon called polarization of light.

Rasmus Bartholin discovered (in 1669) that when an ordinary ray of unpolarized light is made incident on a cristal (polarizer) it is refracted into two rays ordinary ray (o-ray) and extraordinary ray (E-ray) . Polarizers use this property.

Suppose you have two such polarizer with their principle section at $60^\circ$ to each other. An unpolarized light of intensity $8 mW/cm^2$ passes through that combination, what will be the intensity of the transmitted light (in $mW/cm^2$ )?