The U.S. nuclear industry needed about 10,000 tons per year of U3O8 in 1970. Assuming that enrichment and tails requirements do not change and the industry increases at a rate of 2% per year, how long would it take for the $140/kg U reserves to be exhausted? Assume that the reserves are 600,000 tons of U3O8. Develop a formula that will be able to relate the length and increasing rate as well.