plot z=exp(-((x-4)^2+(y-4)^2)^2/1000) + exp(-((x-12)^2+(y-12)^2)^2/1000) + exp(-((x+4)^2+(y+4)^2)^2/1000) + 0.1(exp(-((x+4)^2+(y+4)^2)^2)+exp(-((x-12)^2+(y-12)^2)^2) + exp(-((x-4)^2+(y- 4)^2)^2))