  We devise a fairly general method for estimating the size of quotients
between algebras of functions on a locally compact group. This method is based
on the concept of interpolation sets and unifies the approaches followed by
many authors to obtain particular cases.
  Among the applications we find, we obtain that the quotients WAP(G)/B(G) (G
being a locally compact group in the class [IN] or a nilpotent locally compact
group) and CB(G)/LUC(G) (G being any non-compact non-discrete locally compact
group) contain a linearly isometric copy of \ell_\infty(\kappa(G)) where
\kappa(G) is the compact covering number of G, and WAP(G), B(G) and LUC(G)
refer, respectively, to the algebra of weakly almost periodic functions, the
uniform closure of the Fourier-Stieltjes algebra and the bounded right
uniformly continuous functions.
