If n(A)=pn(A)=pn(A)=p and n(B)=qn(B)=qn(B)=q, how many functions f:A→Bf: A \to Bf:A→B are possible?
pqp^qpq
qpq^pqp
p×qp \times qp×q
2pq2^{pq}2pq