If R is a domain (integral domain), prove that there is no subfield K of Frac(R) such that

$\displaystyle

R\subseteq K \subset Frac(R)$

Note: in the book the part that K is a subset of Frac(R) they used some funny notation, that basically looks like subset or equal to, but the line that means equal to was crossed out.... I just assumed that they mean the subset, which doesn't equal K.... but I'm not sure