The external and the internal radii of a hollow right circular cylinder of height 15 cm are 6.75 cm and 5.25 cm respectively. If it is melted to form a solid cylinder of height half of the orignal cylinder, then the radius of the solid cylinder is
In the following figure, rectangle represents Opticians, circle represents Curators, triangle represents Campers and square represents Europeans. Which set of letters represents Opticians who are either Europeans or Campers?