Need help in select statement from two tables

Hi,

Good day!

I have a problem in my select query statement to get the value of reject from op_reject table and spv_reject table in one row

here is my query:

SELECT o.compound_type, SUM(o.reject) AS op_reject, s.compound_type, SUM(s.reject) AS spv_reject
FROM op_reject AS o ,spv_reject AS s
WHERE o.compound_type = 'P28' AND s.compound_type = 'P28'
AND o.process_id = '2' AND s.process_id = '2'
AND o.reject_date = '2013-09-30' AND s.reject_date = '2013-09-30' 
GROUP BY  o.compound_type, o.process_id;

Code (markup):

this code has an output:

P28|6.00|P28|6.00

but it should only be:

P28|3.00|P28|3.00
because the sum of rejects are only 3.00

I attached my database for your reference.

Any help is highly appreciated.

Thank you so much.