Help with Query

Hello,

I have a table such as,

Seq Typ rate
1 buy 5
2 sell 4
3 buy 5
4 sell 0
5 buy 4
6 sell 5

can someone please help me with a query, that fetch only those rows where type 'buy' and rate is not 0 and
type 'sell' and rate is 0

Thanks
Pavan