SQL & PL/SQL

A batch may consist of a number of jobs running. So I have a batch
table and a jobs table as follows:

SQL> desc batch
 Name                                      Null?    Type
 ----------------------------------------- -------- ------------------
 BATCH_ID                                  NOT NULL NUMBER
 BATCH_LATEST_JOB_ID                         NOT NULL NUMBER
) <br/>

SQL> desc jobs
 Name                                      Null?    Type
 ----------------------------------------- -------- ----------------------------
 JOB_ID                                    NOT NULL NUMBER
 BATCH_ID                                           NUMBER
 <br/>

Now I also have a job_time table that gives me the start and end time for
the jobs.Here is the structure.

SQL> desc jobs_time
 Name                                      Null?    Type
 ----------------------------------------- -------- ----------------------------
 JOBS_LOAD_ID                              NOT NULL NUMBER
 START_TIME                                NOT NULL DATE
 JOB_ID                                    NOT NULL NUMBER
 END_TIME                                           DATE
 

I need the time diff between the
1st job (min jobsload id) of a particular batch
and the end_time (for BATCH_LATEST_JOB_ID). How can I do that?