Carbon-14, or 14C , has a half-life of 5,730 years. It is constantly being created in the atmosphere though collisions between cosmic particles and atmospheric nitrogen. Because of this, living plants and animals constantly exchange amounts of 14C with the environment. When the plant or animal dies, it no longer absorbs 14C, and the amount left in it decreases due to radioactive decay. The age of organic materials can then be determined by measuring the activity of 14C decay, a process known as radiocarbon dating. Suppose an archaeologist finds an ancient firepit containing partially consumed firewood, and the 14C content of the wood is only 28.8% that of an equal carbon sample from a present-day tree. What is the age of the wood (in yr)?