What is the output resistance, When we observe in a common emitter circuit the collector current increase from $9.5 \;mA\;to 10\;mA$ When the collector voltage increase from $2.5 \;to \;6v$ When base current is kept constant .

Question

$(a)\;7.5 K\; \Omega \\ (b)\;8.5 k \; \Omega \\ (c)\;3.2 k \;\Omega \\ (d)\;7.0 k\; \Omega$