TABLE : <http://pastie.org/6205255>

How to show tutor name who has max(sum(time))?

First I tried this:

```
select max(sum(time))
from tutorial
group by tutor;

```

the answer is 5
its just shown the max time but not shown who has the time(tutor name)
i tried to add select tutor, max(sum(time)) .... but ERROR

second, I tried this: (separation between max and sum)

```
select max(x) "THE MAXIMUM"
from (
    select sum(time) x,tutor from tutorial group by tutor
);

```

answer = 5.
I tried to write `select tutor,max(x) "THE MAXIMUM" ......` but still error

ALL OF THEM HAS SAME ERROR.
THE ERROR SAYS :

```
ORA-00937: not a single-group group function
00937. 00000 -  "not a single-group group function"

```

please help me