$27.$ Viewed at night from the high diving board at a swimming pool, the light from an underwater

bulb forms a bright, $10$ ft$.$ diameter circle on the surface of the water $(=1\mathrm{.}33).$ How far

below the pool's surface is the bulb? $($Hint: The refracted beam is transmitted parallel to the

air$-$water interface.$)$

A$)4\mathrm{.}4$ ft$.$

B$)8\mathrm{.}8$ ft$.$

C$)3\mathrm{.}8$ ft$.$

D$)6\mathrm{.}7$ ft$.$

E$)7\mathrm{.}5$ ft