At the start of 2014, the world’s known copper reserves were 690 million tons. With t in years since the start of 2014, copper has been mined at a rate given by 17.9e^0.025t million tons per year.
(a) Assuming that copper continues to be extracted at the same rate, write an expression for the total quantity mined in the first T years after the start of 2014.
(b) Under these assumptions, when is the world predicted to run out of copper?