How many maximum 10Gb ports can plug into Dell server R730

We are going to buy some Dell R730 for our project. But we need 20 port ( type is Optical 10 Gbps ports) on each server.                                                                                

Could you please advise me it is possible 20 ports  10Gb on one server or not?

How many  maximum 10Gb ports can plug into Dell server R730; and what kind of NIC can use to get maximum ports. 

Thank you.