[问答题]
Consider the graphs :ceka q79r wc6g4tf6t.99momjlbp yg/ 1f7p wof $y=-\frac{1}{2}|x|$ and y=2|x|-a , where $a \in \mathbb{Z}^{+}$ .
1. Sketch the graphs on the same set of axes.
2. Given that the graphs enclose a region of area 40 square units, find the value of a .
