We are given the function $f(t) = 67000e^{-0.19t}$, and we want to express it in the form $f(t) = ab^t$.

Step-by-step process:

1. The given function is in the form $f(t) = 67000 \cdot e^{-0.19t}$.
2. We know that the natural base $e$ can be expressed in terms of base $b$ using the following identity: $e^x = b^{x \cdot \ln(b)}$ To express $e^{-0.19t}$ in terms of another base, recall that $e^{x} = (e^{\ln(b)})^{x/\ln(b)}$, and so we multiply out the powers accordingly.

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