Question: Natural Resources

According to the U.S. Energy Information Administration's Annual Coal Report, 896 million short tons of coal were mined in the U.S. in 2016. In addition, U.S recoverable reserves (i.e., what can still be mined starting January 1, 2017) were estimated to be 477 billion short tons, and U.S. "ultimate production" (total amount of coal produced from all coal fields over their entire lifetime, i.e., also taking into account the coal already mined) was estimated to be twice this amount. Based on these assumptions and assuming that the production of coal is defined by Hubbcrt's curve:

1. In what year would we expect the total U.S. reserves to be 84% exhausted?

2. When this happens (or when it happened), what will U.S. annual production be (or what was it)?

3. Give two reasons for not being too surprised if our prediction for part (a) turned out to be false.