Aura,Witherbloom Student

When Aura enters the battlefield, if you used {g} to pay the {b/g} in its mana cost create two Pest token creatures 1/1 with "When this creature dies, you gain 1 life", if you used instead {b} to pay the {b/g} in its mana cost create two Zombie token creatures 2/2.
Whenever a creature dies create a Zombie token 2/2 for each creature which died.