Find the exact value of c>0\displaystyle {c}>{0} such that the area of the region enclosed by the parabolas y=x2c2\displaystyle {y}={x}^{{2}}-{c}^{{2}} and y=c2x2\displaystyle {y}={c}^{{2}}-{x}^{{2}} is 40\displaystyle {40}.

c=\displaystyle {c}=