SQL & PL/SQL :: Mutating Error?

1.I have created table emp_log using structure of emp table

create table emp_log
as select * from emp
where 1=2;

2.Now I have added some new fields i.e
new_sal(updated salary) ,
upd_by (who updated),
upd_date (Salary update date)
alter table emp_log
add (new_sal number, upd_by varchar2(20),upd_date date);

3. I have made following trigger to insert old and new values (for salary,user and date) in emp_log table whenever I update sal for particular employee in emp table and at the same time i am selecting the updated value of sal into lv_sal variable which will cause mutating error.

create or replace trigger emp_trg
after update of sal on emp
for each row
declare

[code]...

4. Suppose sal of emp is 1000:-
update emp
set sal=sal+100
where empno=7369;
>select * from emp_log;
output:- sal= 1000 new_sal=1100

[code]...

Now the question starts if i commment pragma autonomous_tansaction and commit statement then it gives mutating error because at the same time i am updating and selecting value of sal from emp table.

create or replace trigger emp_trg
after update of sal on emp
for each row
declare

[code]...

Questions:-
1.Is pragma autonomous_transaction handling the mutating error and if yes then how?
2.How many ways are there to handle mutating error.
3.What is the exact definition of Mutating Error.
4.An example or query to use lv_sal variable for printing new updated sal.
5.What is Mutating Table , Is it similar to mutating error (Found this topic while searching for mutating error).