GROUP BY and SUM in Crystal Report

I need to do something relatively simple with Crystal Report but I can not.

I have a report like this:

OP   |    CLIENTE   |   PREÇO
1          João          10
1          João          20
1          João          30
2         Marcelo        15
3         Rodrigo        35 
3         Rodrigo        15
4         Pâmela         27

And I would like it to look like this:

OP   |    CLIENTE   |   PREÇO
1          João          60
2         Marcelo        15
3         Rodrigo        50 
4         Pâmela         27

That is, group by OPs and add the prices.

How do I do this ??