SQL & PL/SQL :: How To Sum Data Of One Table Into Another

I have this table that stores following information

SQL> select * from data1;

CUST_ID IU OHB
--------- ----- ----------
001 1 10
001 2 10
001 3 20
001 5 25
002 4 30
003 7 10
003 8 35
004 11 40

8 rows selected.

I need to insert data from this table to another table. ( result1)

SQL> desc result1
Name Null? Type
----------------------------------------- -------- ---------------------------

CUST_ID CHAR(9)
SUM_OHB NUMBER

The output when result1 is queried should look like

SQL> select * from result1;

CUST_ID SUM_OHB
--------- ----------
001 65
002 30
003 45
004 40

Want to do in PL/SQL.

I have tried to simplified my original requirement. This is crux of that. Can not post other details.

Edited to add create and insert script

create table data1( cust_id char(9), iu char(5), ohb number);
INSERT INTO DATA1 ( CUST_ID, IU, OHB ) VALUES (
'001 ', '1 ', 10);

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