i still remember that the question didn't state the distribution of x, so it may not appropriate to use standard normal.
chebyshev inequality can apply on any distribution, so it is only choice
BTW, when will the result be released
i have signed on question book while didn't sign on answer sheet...
I dont know whether I have missed the signature or the signature is not required on answer sheet.
I afraid the GARP wont mark my answer sheet if signature is missed