Small lights are hung on a string 6 inches apart in the order red, red, green, green, green, red, red, green, green, green, and so on continuing this pattern of 2 red lights followed by 3 green lights. How many feet separate the third red light and the 21st red light?Note: 1 foot is equal to 12 inches.<spanclass=′latex−bold′>(A)</span>18<spanclass=′latex−bold′>(B)</span>18.5<spanclass=′latex−bold′>(C)</span>20<spanclass=′latex−bold′>(D)</span>20.5<spanclass=′latex−bold′>(E)</span>22.5