Two identical resistors of 20 ohm each are connected in parallel. This combination, in turn, is connected to a 10 ohm resister. The equivalent resistance of the combination will be
A well of diameter 3 m and depth 14 m is dug. The earth, taken out of it, has been evenly spread all around it in the shape of a circular ring of width 4 m to form an embankment. Find the height of embankment?