With $10\:V$ dc connected at port A in the linear nonreciprocal two-port network shown below, the following were observed:
- $1\: \Omega$ connected at port B draws a current of $3\:A$
- $2.5\: \Omega$ connected at port B draws a current of $2\:A$
For the same network, with $6\: V$ dc connected at port A, $1\:\Omega$ connected at port B draws $\frac{7}{3}\:A$. If $8\:V$ dc is connected to port A, the open circuit voltage at port B is
- $6\:V$
- $7\:V$
- $8\:V$
- $9\:V$