function b0=cmsolv(m,lev,f)
% CMSOLV Solve coarse-level problem in two-level Schwarz method.
%
% function b0=cmsolv(m,lev,f)
%
global ac zm lc ac lc uc
[ph,pv]=size(ac);
rcx=zeros(m*m,1); rcx=f(:); rc1=zm'*rcx; b0=f;
uc0=lc\rc1; uc1=uc\uc0;
tmp=zm*uc1;
b0(:)=tmp;