Complex Query Help

Hello all,

I have a table of work shifts. It has
Table "teams"
Attribute | Type | Modifier
------------+---------------+----------
team_id | varchar(50) |
team_name | varchar(100) |
location | varchar(100) |
department | varchar(100) |
shift | varchar(100) |
start_time | numeric(30,6) |
end_time | numeric(30,6) |
mon | boolean |
tue | boolean |
wen | boolean |
thu | boolean |
fri | boolean |
sat | boolean |
sun | boolean |
start_day | char(3) |
end_day | char(3) |

What I need to be able to do is select team_name where team works between a
time span ie teams that work between 730 and 1600 how would I do this????
What type of field should i sue for start_time and end_time?