Finding the largest value

Hi

I need a formula to find the largets value for a firm. This is best shown by an example. I have a list of firms 3000 firms, each firm has a number of shareholders witha percentage: e.g

Firm %owned
1 20
1 30
1 50
2 0.3
2 20
2 13
3 100
4 20
4 2
4 25


I need a formula that works out the largest shareholder.... in my example it would look like:

Firm Largest Owner
1 50
2 20
3 100
4 25


Thanks very much for your help!!!

Use this array formula

=MAX(IF(A2:A20=firmid,B2:B20))

That's worked perfectly, thankyou!