SQL Query to SUM Columns of 2 different tables

Sir,

i have  two table

the table1 is payment table with following data

id  Total   paid   balance            

1    4500   4500     0

the 2nd table is payment history with following data

id  Total   paid   balance            

1    4500   0     4500

1     4500  4500   0

i want sum of total,sum of balance from table 1

and sum of paid from table2. like below

total  paid balance

4500  4500    0

I am usin g following query for get this result

select SUM(a.total),SUM(b.paid),SUM(a.balance) from payment a join paymenthistory b on a.req_no=b.req_no

but it gives following result

total  paid balance

9000 4500    0

how to get sum from two different  tables.?