[问答题]
Consider the graphs of*+ ks 9ruov 78lufwl /5rad-ojxm (;ln,w)o7l q9z ky4w f0vsj(kw7 sw $y=-\frac{1}{2}|x|$ 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 .
