Help with developing a program code

I´m trying to write a function which will calculate y to given conditions. Can you help me to fill in function?

function [y]=f(x)

if x>=9

        y = 15*(4*x)^(1/2)+10;
end

if (0<=x<9)

         y=10*x +10;
end

if (x<0) y=10;

end