Given the following relation table R, S, and T as follows:

R

A	B
a1	b1
a2	b1
a3	b1
a1	b2
a2	b2
a3	b2
a1	b4
a2	b4

S

A

a1

a3

T

B

b2

b4

Please give the result of table S divided by table T (S T).

Group of answer choices

A

a1

a2

Undefined.

B

b1

b2

B

b1