Need help with this word problem that includes the gas laws?

Question

A 16L fire extinguisher contains 15.0L of water and 1.00L of compressed air. In order to operate efficiently, the last drop of water must be expelled at 110 kPa. Assuming that the temperature is constant, the pressure must be:

A)117 kPa

B) 1.65 MPa

C) 176 kPa

D) 1.76 MPa

Please help me =(

Thanks to all who contributed!!

Answer 1

At constant temperature, if the  Volume of air is going to increase by 16 times, the pressure will decrease by 16 times. (Boyle's Law).

110kPa x 16 = D: 1.76MPa.

Answer 2

Just before expelling the last drop, the gas has expanded to 16.0 L.

Take it from there. Use Boyle's Law since T is constant.