How to put a value in a plot label?

I have a surf plot where one fixed variable changes and each one is apart of a subplot. I would like the title of each subplot to reflect the fixed variable at that instance. My code currently is:

for k = 1:4
    kd = 0.0143.*5*k;
    SOTE = (a + kd + kp).*X.^beta.*5*k;
    figure(1)
    if k < 3
    subplot(4,1,k)
    surf(X, Y, SOTE)
    title('Depth = (varying number here) ft');
    xlabel('Flux (scfm)');
    ylabel('AT/AD');
    zlabel('SOTE (%)');
    grid on
    else
    subplot(4,2,k)
    surf(X, Y, SOTE)
    title('Depth = (varying number here) ft');
    xlabel('Flux (scfm)');
    ylabel('AT/AD');
    zlabel('SOTE (%)');
    grid on
    end
end

In each subplot the depth is 5, 10, 15, 20 respectively.

Answer 1

[Alex Sune]

depth = [5,10,15,20];
for k = 1:4
    kd = 0.0143.*5*k;
    SOTE = (a + kd + kp).*X.^beta.*5*k;
    figure(1)
    if k < 3
    subplot(4,1,k)
    surf(X, Y, SOTE)
    title(['Depth = ' num2str(depth(i)) ' ft']);
    xlabel('Flux (scfm)');
    ylabel('AT/AD');
    zlabel('SOTE (%)');
    grid on
    else
    subplot(4,2,k)
    surf(X, Y, SOTE)
    title(['Depth = ' num2str(depth(i)) ' ft']);
    xlabel('Flux (scfm)');
    ylabel('AT/AD');
    zlabel('SOTE (%)');
    grid on
    end
end

[Jesse Finnell]

A condensed version of the above code

depth = [5 10 15 20];
for k = 1:4
    kd = (-0.001+0.0153)*depth(k);
    SOTE = (a + kd + kp).*X.^beta*depth(k);
    figure(1)
    subplot(2,2,k)
    surf(X, Y, SOTE)
    title(['Depth is ',num2str(depth(k)),'ft']);
    xlabel('Flux (scfm)');
    ylabel('AT/AD');
    zlabel('SOTE (%)');
    grid on
end