Answer: 500Pa
Step-by-step explanation:
Using Boyle's law which is a gas law, it states that the pressure and volume of a gas have an inverse relationship. That is to say, If volume increases, then pressure decreases and vice versa, when temperature is held constant. Therefore, when the volume is halved, the pressure is doubled; and if the volume is doubled, the pressure is halved.
So in this case, since the temperature is held at constant (off) the value of the pressure is half the value of the volume plunger, being 500Pa