How much more gas (in gallons) will he get for $20 USD if he buys the gas before crossing the border instead of buying it in Canada? (1.000 liter = 0.264 US gallons)

The big bang nucleosynthesis theory states that elements were produced in the first few minutes of the big bang while elements have their origins in the interiors of stars, forming much later in the history of the universe.

Iwould appreciate if someone could me.

Which change to the system wood cause the freely-moving piston to lower?