如图,在三棱柱\(ABC-{{A}_{1}}{{B}_{1}}{{C}_{1}}\)中,\(AB\bot \)平面\(A{{A}_{1}}{{C}_{1}}C\),\(A{{A}_{1}}=AC\)\(.\)过\(A{{A}_{1}}\)的平面交\({{B}_{1}}{{C}_{1}}\)于点\(E\),交\(BC\)于点\(F\).
\((\)Ⅰ\()\)求证:\({{A}_{1}}C\bot \)平面\(AB{{C}_{1}}\);
\((\)Ⅱ\()\)求证:\({{A}_{1}}A\,{/\!/}\,EF\);
\((\)Ⅲ\()\)记四棱锥\({{B}_{1}}-A{{A}_{1}}EF\)的体积为\({{V}_{1}}\),三棱柱\(ABC-{{A}_{1}}{{B}_{1}}{{C}_{1}}\)的体积为\(V.\)若\(\dfrac{{{V}_{1}}}{V}=\dfrac{1}{6}\),求\(\dfrac{BF}{BC}\) 的值.