Answer
He must have pressed "ln" instead of "log" (on the calculator).
Work Step by Step
$\log 79$ is, as we found in exercise 75, between 1 and 2, because
$79$ is between $10^{1}$ and $10^{2}$.
The calculator has buttons for $\log$ and $\ln$ close to each other, so let us check whether 79 is between $e^{4}$ and $e^{5}.$
$e^{4}\approx 54.598$
$e^{5}\approx 148.413,$ and 79 is really between these two powers of e.
This means that the NATURAL logarithm, $\ln 79$ is between 4 and 5.
He must have pressed "ln" instead of "log".
