function e=rminf(c,t)
% rminf: used to find the minimum reflux ratio in ideal binary distillation
% function e=rminf(c,t)
%  c: p, xf, q
ks=kval(t,c(1));
x1=(1-ks(2))/(ks(1)-ks(2));
x2=c(2)/(1+(ks(1)-1)*c(3));
e=x1-x2;
