The respiratory exchange ratio (rer) is a way of determining the body's metabolism of:

The respiratory   exchange ratio  (RER)   is  a  way  of   determining  the   body  metabolism  of  carbohydrate  and  fat.
   The   respiratory   exchange  ratio   is  the ratio  between  the  amount  of  carbon  dioxide  produced  and  oxygen  used. Measuring  this  ratio   can  be  used  to  estimate  the  respiratory  Quotient (RQ)  which  an  indicator  of  which  carbohydrate or  fat  is  being metabolized  to  supply  the   body  with    energy.

Are you asking about a street map usage  if so here is your answer  a street map for a very limited area could simply be a bit map or a .jpg image.  but a more general map would probably store the streets as vectors.  but you shouldn't assume that there is one way to do it

Country b may have shorter life expectancies. country a has more literate people. country a has better health care system. apex