During inhalation, a person's diaphragm and intercostal muscles contract, expanding the chest cavity and lowering the internal air pressure
below ambient so that air flows in through the mouth and nose to the lungs. Suppose a person's lungs hold 1300 mL of air at a pressure of
1.00 atm. If they expand their chest cavity by 460 mL while keeping their nose and mouth closed so that no air is inhaled, what will be the air
pressure in their lungs in atm? Assume the air temperature remains constant.

a and b sometimes have a positive value

it's when something is going so fast it makes a loud noise, breaking the sound barrier, for example: a jet makes a loud noise, not only cause of the jet but because they reached a point where they went so fast that you can year the noise from various parts, kinda like a police car, lets say the car was going   so fast that you hear the siren of the cop car right next to you, but the car is probably a mile a way, it's cos the siren was next to you a few seconds if you understand me

i would say