order priority

Hello Everyone,

recently i was asked about order priority and i had no clue on it, can someone please through some light on it, or point me where i can find more info on it.

the scenario was that if there 2 orders created in morning, one with 70 pcs and one with 80 pcs and if there was no stock availaible , but then same day afternoon 100 pcs come in, which order will go out first and why?, and what will happen to 2nd order, can you guys explain that.

thanks in advance

dilip