8.
已知抛物线\(W\):\(y^{2}=4x\),直线\(x=4\)与抛物线\(W\)交于\(A\),\(B\)两点\(.\)点\(P(x_{0},y_{0})(x_{0} < 4,y_{0}\geqslant 0)\)为抛物线上一动点,直线\(PA\),\(PB\)分别与\(x\)轴交于\(M\),\(N\).
\((\)Ⅰ\()\)若\(\triangle PAB\)的面积为\(4\),求点\(P\)的坐标;
\((\)Ⅱ\()\)当直线\(PA⊥PB\)时,求线段\(PA\)的长;
\((\)Ⅲ\()\)若\(\triangle PMN\)与\(\triangle PAB\)面积相等,求\(\triangle PMN\)的面积.