I have a problem with these two questions.. I need help in solving them, what equation do I use etc..

A three-phase half-wave rectifier circuit is supplied from a 120/208 V 3phase, 60 Hz source. Determine the average DC output voltage of the rectifier.

Answer:140.3

A three-phase half-wave rectifier circuit is supplied from a 120/208 V 3phase, 60 Hz source. What is the frequency of the output ripple voltage.

Answer:180hz

I spent 2h looking for the equations and explanation but with no results..

Can someone briefly explain how to solve them?

Thanks in advance!

/Peter