The Lunge feat is described as follows:
You can increase the reach of your melee attacks by 5 feet until the end of your turn by taking a –2 penalty to your AC until your next turn. You must decide to use this ability before any attacks are made.
The Whirlwind Attack feat is described as follows:
When you use the full-attack action, you can give up your regular attacks and instead make one melee attack at your highest base attack bonus against each opponent within reach. You must make a separate attack roll against each opponent.
When you use the Whirlwind Attack feat, you also forfeit any bonus or extra attacks granted by other feats, spells, or abilities.
Reach weapons are described as follows (emphasis added):
A reach weapon is a melee weapon that allows its wielder to strike at targets that aren't adjacent to him. Most reach weapons double the wielder's natural reach, meaning that a typical Small or Medium wielder of such a weapon can attack a creature 10 feet away, but not a creature in an adjacent square. A typical Large character wielding a reach weapon of the appropriate size can attack a creature 15 or 20 feet away, but not adjacent creatures or creatures up to 10 feet away.
Suppose I am a medium character armed with a reach weapon. There are some enemies 10 feet away from me, and some enemies 15 feet away.
I use Lunge and Whirlwind Attack. Which enemies do I make attacks against?
(a) Only the enemies 15 feet away.
(b) The enemies 10 feet away and the enemies 15 feet away.