Creating payment transaction

[mk44]

Hi,

I am newbie in this and I am trying to make small app for sending money using rippleApi. I have few questions on which I could not find answer on forums and did not understan reading ripple documentation. Questions are:

1. How can I create payment transaction in sending USD, currently I can do it but just sending XRP?

2. I used method for generating new account, so I create account which currency is XRP,  should I somehow set some other curreny as default for account in order to create payment wher transaction is using different currency?

3. How can I create transaction where source send amount in USD  whine destination get amoun in EUR?

Thank you