Find intersection between a line and a curve

I've some points and I've plotted the interpolation between these points x = [94.8;84.4;63.1;49.4;40.6;33.8;23.2;20.1;10.2;9.2;7.9]; y = [0; 11.4;29.7;41.6;47.5;50.1;52.9;50.6;32.2;28.1;0]; f=@(xi)(interp1(x,y,xi,'spline'))

Now I want to find the intersection to another line (for example y = mx+C), and it might intersect twice.