Excited about the success of celebrity stamps, post office officials  were  rumored  to  have  put  forth  a  plan  to institute   two   new   types   of   thermometers.   On   these new  scales, E° represents    degrees    Elvis    and    M° represents   degrees   Madonna.   If   it   is   known   that  40°E = 25°M,  and 280°E = 125°M; and    degrees    Elvis    is linearly  related  to  degrees  Madonna, write  an  equation expressing  E in terms of M.