Formula to add cells based on like values and populated cells

Due to my inexperience with formulas, I am not certain how to word my question.....

Please see the attached document for further clarification.

I need an ongoing total of the amt of footage (C) need for each type of cable (E) that has not yet been completed (I). So, if column I is blank, I need to add up the footage in column (C) but only for like cable types in column (E).

I would like to be able to glance at this spreadsheet and know how many feet of 0.625 cable and how many feet of 0.875 cable is needed for the pending (incomplete) jobs on any given day.

Any input would be appreciated. I would be happy to have the formula needed as well as an explanation.

sample.xlsx

I would recommend using the =SUMIFS function.

Setup summary fields, one for each type of Cable.

Total of 0.625 required: =SUMIFS(C:C,I:I,"",E:E,0.625)
Total of 0.875 required: =SUMIFS(C:C,I:I,"",E:E,0.875)

Basically, the sumifs function is only going to add up values in the first range (Column C) if it meets the criteria defined in the formula. In this case, I'm telling to see if the corresponding value in column I is blank, and then if the type of cable in column E matches.