How do you know what determinant causes aggregate demand to decrease and short-run aggregate supply to increase?

The question states: Congress votes to cut spending on the space program. I know that AD decreases, and AS increases, but I don't know what the determinant is, or whether I'm supposed to list the determinant for both AD and AS or just one or the other. If it's just one or the other, do I identify the determinant of the line that is decreasing or increasing?