Calculate the parallel value of resistors at base of common emitter amplifier

I don't know if questions can be asked like this here but if they can I want this question. In an exam paper I saw a question to determine the parallel value of the R1 and R2 resistors in the image below but I am not sure how to do this. I tried using the bias equations for a common emitter amplifier but I have not been able to get the answer. I put the exact question in the image below so you can see how exactly it was asked. I am only asking for question c as I have done the first two(I may or not be correct). You do not necessarily need to solve it but if you at least know formula or method I could use it would be very helpful.

What they likely want to ask about is the input resistance seen by the source $V_{in}$.
That means the the input resistance of the amplifier is given by $$R_1 || R_2 || R_{in}$$ where $R_{in}$ is the input resistance of the emitter-degenerate common-emitter amplifier.
So you just have to work out what $R_{in}$ is (you have enough information in your schematic), and then find what needs to be put in parallel with that to get 10 kOhms.