Execution time estimation
There's no list here. In this problem, $a, b, c$ are simply numbers, so the $k$ loop will iterate $c$ times, taking the values $k=1, k=2, \dotsc,k=c$ for any values of $i$ and $j$. Working outwards, the $j$ loop will iterate $b$ times and each time will perform a complete $k$ loop. In other words, the total amount of work done by the $j$ loop will be $bc$: $b$ iterations of the $j$ loop, each involving $c$ steps of the inner $k$ loop, no matter what the $i$ value is. Finally, in a similar way, the outer $i$ loop will iterate $a$ times, each time doing $bc$ work. The total number of iterations, then, will just be $abc$.

For example, with $a=2, b=3, c=2$ the $(i, j, k)$ values will be, in order,
$$\begin{array}{c}
(1,1,1) \\
(1,1,2) \\
(1,2,1) \\
(1,2,2) \\
(1,3,1) \\
(1,3,2) \\
(2,1,1) \\
(2,1,2) \\
(2,2,1) \\
(2,2,2) \\
(2,3,1) \\
(2,3,1) \\
\end{array}$$