Help with Expressions please

[#1]

If I have a table containing data like this:

Please could someone tell me how to write expressions to show:

• The fewest number of minutes spent by anyone on a Problem Code (please note that every time someone spends time on a call it creates a seperate entry, so I would need to sum the time spent for each call linked to the problem code and show the lowest sum) - looking for a team record.
• The fewest number of minutes spent by the individual I am looking at on a Problem Code - looking for a personal best.

Thanks.

[whiteline]

Create two charts. One with [Problem Code] dimension the other with [CallRef] (I guess its an individual).

And use this expression (in both charts):

=Min(aggr([Minutes Spent], [Problem Code], [CallRef])