SAT Functions as Models

Algebra

If the current through a conductor decreases exponentially with time according to the equation $I(t)=I_{0}\left(\frac{5}{4}\right)^{-t},$ where $I_{0}=64$ mA is the initial current, how many seconds after $t=0$ will the current be approximately $26$ mA?

(A) One
(B) Two
(C) Three
(D) Four
(E) Five