[sv-ec] Query on cross

In the following covergroup example:

...
A: coverpoint a { bins b1[] = {0,1, 2, 3} iff x+y; }
B: coverpoint b { bins b2[] = {0,1, 2} iff x; }
cross A, B;
...

Will the values (true/false) of guard expressions for bins
impact the cross-coverage space? Basically, if there is no
guard expressions in the above example, total cross-coverage bins will
be 12.
Even with guard expressions, shouldn't we calculate total
cross-bins as 12, irrespective of the values of guard expressions?
 
Another related question is regarding the creation of cross-bins.
In the preceeding example, if the values for A & B are 0 and 0
respectively but both "x+y" and "x" are false, should we increment
the corresponding crossbin i.e. <b1[0], b2[0]>? I believe we should
not increment in this case. Similarly, if 0 is declared as an
ignore_bin,
we shouldn't increment <b1[0], b2[0]>.

Swapnajit.