How calculate values of column#x in whole rows contain some text? about orgaggregate HOT 1 CLOSED

#+name: mytable
| Task   | State | Duration |
|--------+-------+----------|
| RP-135 | Taken |     5.50 |
| RP-77  | Taken |     1.50 |
| RP-135 | Taken |     4.50 |
| RP-135 | Taken |     1.50 |
| RP-77  | Taken |     1.50 |
| RP-162 | Taken |     6.00 |

#+BEGIN: aggregate :table "mytable" :cols "Task vsum(Duration);f2"
| Task   | vsum(Duration);f2 |
|--------+-------------------|
| RP-135 |             11.50 |
| RP-77  |              3.00 |
| RP-162 |              6.00 |
#+END:

#+BEGIN: aggregate :table "mytable" :cols "vsum(Duration);f2" :cond (string= Task "RP-77")
| vsum(Duration);f2 |
|-------------------|
|              3.00 |
#+END: