AR Bad Debt Provision

select
                ps.customer_id customer_id_ps,
               ps.trx_number trx_number,
               ctt.name   cust_trx_name,
                ps.trx_date   trx_date,
                ps.due_date  due_date,
                ps.invoice_currency_code  invoice_currency_code,
                ROUND(ps.amount_due_original * nvl(ps.exchange_rate,
                                         decode(ps.invoice_currency_code,
                                                :functional_currency_code,1,
                                                null)), 2)  amount_due_original,
                ROUND(ps.amount_due_remaining * nvl(ps.exchange_rate,
                                         decode(ps.invoice_currency_code,
                                                :functional_currency_code,1,
                                                null)), 2)  amount_due_remaining,
                ROUND(ps.amount_due_remaining * nvl(ps.exchange_rate,
                                         decode(ps.invoice_currency_code,
                                                :functional_currency_code,1,
                                                null)) *
                        (1 - :percent_collectable / 100), 2) provision,
                to_char(cct.collection_forecast) ||
                        decode(cct.collection_forecast,
                                null,'',
                                '%')  forecast_percent,
                cct.forecast_date  forecast_date,
                AR_ARXBDP_XMLP_PKG.D_Amount_Due_OriginalFormula(ROUND(ps.amount_due_original * nvl(ps.exchange_rate,
                                         decode(ps.invoice_currency_code,
                                                :functional_currency_code,1,
                                                null)), 2)) Temp
from
                ar_customer_call_topics cct,
                ra_cust_trx_types       ctt,
                ar_payment_schedules    ps
        where
                ps.cust_trx_type_id = ctt.cust_trx_type_id(+) and
                ps.payment_schedule_id  = cct.payment_schedule_id(+) and
                ps.class               != 'GUAR' and
                not exists (
                        select 'x'
                        from ar_customer_call_topics cct2
                        where cct2.payment_schedule_id = ps.payment_schedule_id
                        and   (cct2.call_date > cct.call_date
                                OR   (cct2.call_date = cct.call_date
                                and   cct2.customer_call_topic_id >
                                        cct.customer_call_topic_id))) and
                ps.status || ''         = 'OP'
 and ps.customer_id=:customer_id
order by
               -- ps.trx_number
               1,2,3,4,5,6,7,8,9,10,11