Sql server(BOM) material product quantity calculation by multiplier

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SQL-Server

Regarding the Assy Managment in Manufacturing, I have a sample table bellow.

ID ParentID Product AssyQty Description 
1   0        A      1      Finished Good
2   1        A1     2      one A product needs two A1 Products 
3   1        A2     2      one A product needs two A2 Products
4   2        A3     2      one A1 products needs 2 A3 Products 
5   3        A4     2      one A2 product needs 2 A4 Products

It's just the sample and the product can be in much deeper level. In case they need to produce ten A Products then I want to input @Product ='A' and @Muliplier =10 I need bellow result

Product AssyQty Quantity Need 
A1      2        20 
A2      2        20 
A3      2        40 
A4      2        40

What I have tried:

I do not how to calculate to recursive using SQL server
Anyone can support me solve above query? Thank you