A circular park of radius 20m is situated in a colony. Three boys Ankur, Syed and David re sitting at equal distance on its boundary each having a toy telephone in their hand to talk each other. Find the length of the string of each phone.

Question

$( A ) 30\sqrt{3}m \\ ( B ) 20\sqrt{3} m \\ ( C ) 20 m\\ ( D ) 50m$