Given:
\[
a = \log 2,\quad b = \log 3,\quad c = \log 4 = \log (2^2) = 2\log 2 = 2a
\]
Let’s compute:
\[
\log(abcd) = \log a + \log b + \log c + \log d
\]
Assuming \( d = \log 1 \) is implied or undefined. If \( d = \log 1 = 0 \), discard.
But in the context of the question, probably asking:
\[
\log(abcd) = \log(\log 2 \cdot \log 3 \cdot \log 4)
\Rightarrow a + b + c = \log 2 + \log 3 + \log 4 = \log(2 \cdot 3 \cdot 4) = \log 24
\]
\[
{\log 24}
\]