Subtotal column based on time and text column

I have a data that looks like this

Date | Time | Text | Sum
1-1-2001 | 12:23:34 | a| 2
1-1-2001 | 12:23:34 | b| 3
1-1-2001 | 12:25:34 | a| 2
1-1-2001 | 12:26:34 | b| 2
1-1-2001 | 13:23:34 | a| 1
1-1-2001 | 13:24:34 | a| 2

I need a result with something like this
Text | Sum
a | 4
b | 5
a | 3

or even just the sum column.

The first and third row are grouped because they are within a 5 minute range. Similarly with 2, 4  and 5,6. My end goal is to determine the frequency of each sum value in the data. It is a large dataset with multiple text values and date values.