3)Mikhail Kalashnikov invented the AK-47 assault rifle during World War II. Within 50 years, over 100 million AK-47s were produced. In the early 2000s, Russian arms manufacturer Izhmash owned patents to the AK-47. However, the US government bought AK-47s from unlicensed manufacturers in Bulgaria, Hungary, and Romania for its allies in Afghanistan and Iraq.

Use the AK-47 to explain how engineering design is a public good.

Patents are only effective within national jurisdiction. Explain how manufacturers outside Russia could free-ride on the AK-47 design.

Arms expert Maxim Piadiyshev remarked that, with just eight moving parts, the AK-47 was very simple to produce, use, and maintain. How did this simplicity affect Izhmash's sales?

Please give correct answer with explanation.