Characteristic impedance of a transmission line is $50 \Omega$. Input impedance of the open-circuited line is $Z_{a^{-}}=100+j 150 \Omega$. When the transmission line is short- circuited, then value of the input impedance will be
- $50 \Omega$
- $100+j 150 \Omega$
- $7.69+j 11.54 \Omega$
- $7.69-j 11.54 \Omega$