For this case, the first thing you should do is define a reference system.
Once the system is defined, we must follow the following steps:
1) Do the sum of forces in a horizontal direction
2) Do the sum of forces in vertical direction
The forces will be balanced if for each direction the net force is equal to zero.
The forces will be unbalanced if for each direction the net force is nonzero.
Answer:
Add the forces in the horizontal and vertical directions separately.
The volume decreases, by a factor of
(the original pressure/(125 kPa).
Change the 8 pounds to kilograms (divide it by 2.2). Then multiply the kg by the speed of light (300,000,000 m/sec) squared. You get a very big number. It's the number of joules of energy equivalent to 8 lbs of mass.
That ratio is the efficiency of whatever the power went into and came out of. There's no reason the efficiency has to be expressed as a percentage.