Alleles are

How many phenotypes and genotypes are possible in $ABO$ blood group systems?

In humans,multiple alleles are seen controlling the inheritance of which of the following?

The following table is regarding $ABO$ blood group. Identify $W, X, Y, Z$.

Genotype	Blood group
$I^{A} I^{A}$	$A$
$W$	$A$
$I^{B} I^{B}$	$B$
$X$	$B$
$I^{A} I^{B}$	$Y$
$Z$	$O$

$A$ man with blood group $B$ marries a woman with blood group $A$ and their first child has blood group $B$. What is the genotype of the child?

The genotypes of a husband and wife are $I^AI^B$ and $I^Ai$. Among the blood types of their children,how many different genotypes and phenotypes are possible?