SQL & PL/SQL

I am trying to divide the following data into date buckets computed from the last date. The intent is to find out what was the quantity outstanding at the end of a given period.

create table products_quality(
prod_id as varchar2(10),
qty_outstanding number(5),
qty_date date
);


insert into products_quality values(912649,300,to_date('8/12/2003','mm/dd/yyyy'));
insert into products_quality values(912649,600,to_date('10/20/2005','mm/dd/yyyy'));
insert into products_quality values(912649,450,to_date('11/24/2006','mm/dd/yyyy'));
insert into products_quality values(912649,700,to_date('1/28/2008','mm/dd/yyyy'));
insert into products_quality values(912649,650,to_date('2/17/2008','mm/dd/yyyy'));
insert into products_quality values(912649,700,to_date('4/7/2008','mm/dd/yyyy'));
insert into products_quality values(912649,800,to_date('7/16/2008','mm/dd/yyyy'));
insert into products_quality values(912649,900,to_date('7/31/2008','mm/dd/yyyy'));
insert into products_quality values(912649,950,to_date('12/28/2008','mm/dd/yyyy'));
insert into products_quality values(912649,1000,to_date('1/1/2009','mm/dd/yyyy'));
insert into products_quality values(912649,1100,to_date('1/17/2009','mm/dd/yyyy'));
insert into products_quality values(912649,1500,to_date('2/1/2009','mm/dd/yyyy'));

The result will group by prod_id and show the latest qty_outstanding within each of the date buckets. Kindly note, if there is no data within that bucket then the data from next bucket is chosen (e.g in bucket (31-90 days) below. The last date is the base date and is not counted in the bucket

Prod_id | qty_date | 1-30days | 31-90days | 91-180days | 180-365days | 366-730days | 731-1095days | 1096-1825days
912649 | '2/1/2009' | 1100 | 1000 | 900 | 900 | 700 | 700 | 450 | 600 | 300


Can we write a plain SQL to do it?

Thanks