how to get perticular id based on name priority

[khabaleshri]

Requirement :
If we have multiple source counterparty id for a counterparty name then
1)      Check if trade name is same- if 'yes' then use the max id. If 'no' then follow below steps
a.       If multiple trade names then pick the id from 'A' if 'A' trade name exists
b.       If 'A' source name does not exits then use 'B' id if exists
c.       If 'B' is not available then use 'C' id
d.       If 'C' is not available then use 'D' id

sample date and desired result

Source CPTY ID   CPTY NAME   AMOUNT   Trade Name
13682         ABC      1000                A
5412                 ABC      1000                B
9621                ABC             1000                C
23657        ABC             1000                D
6542                XYZ            2000                B
963241        XYZ             2000               C
785321        XYZ             2000               D
13254       CDF            3000               A
23645       CDF            3000               A
         
Desired result         
Source CPTY ID   CPTY NAME   AMOUNT   Trade Name
13682      ABC               1000   A
6542              XYZ               2000   B
23645      CDF               3000   A

here is my effort :
if
([count source id]>1 and [count trade name]>1)

then
(if ([Trade Name]='A') then (Source Counterparty Identifier]) else if ([Trade Name]='B') then ([Source Counterparty Identifier]) else if ([Trade System Name]='C') then ([Source Counterparty Identifier]) else ([Source Counterparty Identifier]))

else ([max source id])

count source id =count(distinct source counterparty id for cpty name)
count trade name= count(distinct trade name for cpty name)
max source id =maximum(source id for cpty name)

but I am not able to get desired results anyone help me out from this?