To answer this question, we have the following situation:
We need to have the time in minutes as follows:

Now, we have that the unit rate for preparing 24 containers at 7.66666...minutes is:

That is 3.1304...containers per minute. If we inverse this rate, we obtain:

We can convert this time in seconds as follows:

Then, in seconds, we have that the maximum time per container is about:

Or equivalently:
19.16667 sec per container.