A young girl from the Kayan wears a neck ring made of brass. it looks as if there are 21 individual rings but the ring is actually one continuous length of brass fashioned (bent) into a coil. the height of the brass coil is 12 cm and its average circumference is 40 cm. neck rings are usually only removed to be replaced with a bigger one as the girl grows. however, we can estimate the mass of this neck ring without removing it. the coil has a height of 12 cm and the coil has 21 turns. calculate the radius of the brass in cm