Empty set is

Is Axxphi the empty set or not, where phi denotes the empty set and A is any set?

Number of mappings from an empty set to a non empty set with n elements

Is empty set subset to every set?

Is every relation from a non - empty set A to a non - empty set B, a functions from a to B ?

Let X and Y be two non-empty sets such that XnnA=YnnA=phiandXuuA=YuuA for some non-empty set A. Then

If A and B are non-empty sets, then AxxB is a non-empty set of ordered pairs (x,y) such that x inB and yinA .

If A and B are non-empty sets such that A sup B, then

Are two empty sets SetA and SetB equal?