如图\(1\),在高为\(2\)的梯形\(ABCD\)中,\(AB/\!/CD\),\(AB=2\),\(CD=5\),过\(A\)、\(B\)分别作\(AE⊥CD\),\(BF⊥CD\),垂足分别为\(E\)、\(F.\)已知\(DE=1\),将梯形\(ABCD\)沿\(AE\)、\(BF\)同侧折起,使得\(AF⊥BD\),\(DE/\!/CF\),得空间几何体\(ADE-BCF\),如图\(2\).
\((\)Ⅰ\()\)证明:\(BE/\!/\)面\(ACD\);
\((\)Ⅱ\()\)求三棱锥\(B-ACD\)的体积.