We have to remember that exponential decay describes the process of reducing an amount by a consistent percentage rate over a period of time. It can be expressed by the formula
[tex]N(t)=N_0e^{-\lambda t}[/tex]
where N(t) is the quantity at time t, N0 = N(0) is the initial quantity, that is, the quantity at time t = 0, and the constant λ is called the decay constant
Thus, the initial quantity is 800 and the decay constant is 0.123, the exponential decay function is
[tex]y=800e^{-0.123t}[/tex]The correct answer is the first one.
