Hi guys, really stuck on this one.

A 1000N black is to be lifted using a chain sling (as shown). If the tension in the chain sling is not to exceed 1300N, find the shortest sling ABC that can be used.

A is the most left point, B is the most right point and C is the top point.

I think i have to take the derivative of something to find the minimum but have no idea how to go about that.