(2) From the title, we can see that A'D⊥A'E, A'D⊥A'F, A'D⊥ plane A'EF, A'D⊥EF.

, A'D=2, A'E=A'F=3/2, be = BF = 1/4bc = 1/2, ef = 1/2 times the root number 2,

V triangular pyramid A'-EFD=SH/3=S triangle a' ef * a'd/3 =1/2nd radical 17 * 2/3 =1/3rd radical17.