Matlab: how to write a non-uniform diffusion coefficient in a 2D region using pdetool box

I'm solving an advection-diffusion equation using pdetool box . How to make the diffusion coefficient c to be 1 when y>0.03 and 0.2 otherwise. Thanks

    c = 1;
    a = 1;
    f = 0
    d = 1; xmin=0;xmax=0.575;ymin=0;ymax=0.05315;ymax2=0.066; 
    gdm = [3;4;xmin;xmax;xmax;xmin;ymax;ymax2;ymin;ymin]; 
    g = decsg(gdm, 'S1', ('S1')');
    hmax = .1; % element size
    [p, e, t] = initmesh(g, 'Hmax', hmax);
    [p,e,t] = refinemesh(g,p,e,t);
    [p,e,t] = refinemesh(g,p,e,t);
    [p,e,t] = refinemesh(g,p,e,t);
    [p,e,t] = refinemesh(g,p,e,t);
    [p,e,t] = refinemesh(g,p,e,t);
    numberOfPDE = 1;
    pb = pde(numberOfPDE);
    % Create a geometry entity
    pg = pdeGeometryFromEdges(g);
    bc1 = pdeBoundaryConditions(pg.Edges(1),'u',100);
    bc2 = pdeBoundaryConditions(pg.Edges(2),'u',66);
    bc3 = pdeBoundaryConditions(pg.Edges(3),'u',11);
    bc4 = pdeBoundaryConditions(pg.Edges(4),'g',0);
      pb.BoundaryConditions = [bc1,bc2,bc3,bc4]; 
    u = pdenonlin(pb,p,e,t,c,a,f, 'jacobian', 'lumped');
    figure;
    hold on
    pdeplot(p, e, t, 'xydata', u, 'contour', 'off', 'colormap', 'jet(99)');
    title 'chemical Diffusion, Steady State Solution'
    xlabel 'X-coordinate, cm'
    ylabel 'Y-coordinate, cm'