using a graphical tool------ >see attached drawing
points of intersection of parabolas are--------->point P and point Q
point P(-2,-4) point Q(2,-4)
their projections on the x-axis. are---- > point R and point S
point R(-2,0) point S(2,0)
the sides length of of the rectangle are
PQ=RS= 4
PR=QS=4
Perimeter=PQ+RS+PR+QS=16
the answer is 16