Multi Mode synthesis v/s Multi Corner synthesis

 hi,

i just have a simple question that whether RC tool goes for Multi mode synthesis and multi corner synthesis at the same time or not ?

Likewise do we need to do any settings on the same for both the synthesis to take place at the same time or not ?

what all settings are required to go for both type of synthesis if we do it individually ?

which is the BEST type of synthesis out of both the methods ?

thanks 

tanyacool