Difficulty for solving a problem relating to a truss

How can I solve this problem below by the method of section. Because when I made a section, I always found 4 unknown for 3 equations of equilibrium.

Below there are the asking problem plus the answer relating to it for verification, and finally a drawing file attached.
Note: The little circle represent the joints between members on the drawing.
Note: The drawing file is in word97 format for PC and not for MAC.

The asking problem:
The diagonal members in the center panel of the truss shown are very slender and can act only in tension; such members are known as counters. Determine the force in member DE and in the counters which are acting under the given loading.

The answers of this problem: Force in member DE = 0
Force in member BE = 10kips Tension
Force in member EF = 5 kips Tension