Sum of a field on Group of different fields

Hi,

I have a req to add sum of the fields if the respective fields are more than one, else should pass the same field.

Below is the source structure

From that structure for 13thNov I should populate C filed i.e.value is 1.1, 14thNov should be 1.2, 15th Nov should be 2.2. can you please let me know how can I achieve this based on fields of "a" and "d".

Here  "C" vale is being calculated based on unique of "a" and "d".