c1 from 0 to p c2 from p to q c3 from q to 1
the boundary conditions when x=p diff(c1(x,t),x)=(epsilon(s)^B/epsilon(p)^B)*diff(c2(x,t),x)
c1(x,t)=c2(x,t) when x=p
when x=q
diff(c2(x,t),x)=(epsilon(n)^B/epsilon(s)^B)*diff(c3(x,t),x)
c2(x,t)=c3(x,t)when x=q
when x=0 diff(c1(x,t)=0
when x=1 diff(c3(x,t)=0

prime.mw