The amount of carbon dioxide (\text{CO}_2)(CO 2 )left parenthesis, start text, C, O, end text, start subscript, 2, end subscript, right parenthesis in the atmosphere increases rapidly as we continue to rely on fossil fuels. The relationship between the elapsed time, ttt, in decades, since \text{CO}_2CO 2 start text, C, O, end text, start subscript, 2, end subscript levels were first measured, and the total amount of \text{CO}_2CO 2 start text, C, O, end text, start subscript, 2, end subscript in the atmosphere, A_{\text{decade}}(t)A decade (t)A, start subscript, start text, d, e, c, a, d, e, end text, end subscript, left parenthesis, t, right parenthesis, in parts per million, is modeled by the following function: