Which of the following systems undergo a quasistatic process?

(a) A gas-containing balloon is popped inside a vacuum container. System: container, gas, and balloon.

(b) A cup of coffee cools down. System: coffee.

(c) A sample of compressed gas in a cylinder fitted with a heavy piston is allowed to expand, pushing the piston outward. System: gas.

(d) An ice cube melts in a glass of hot water. System: water and ice cube.