a random sample of size 100 is taken from a normal population with SD=25. what is the probability that the mean of the sample will differ from the mean of the population by 3 or more either way?

I calculate it as

P(mean of sample - mean >3)=P(Z>3/2.5)

=P(Z>1.2)=0.1151, but the answer is different. can you tell me where did I get wrong?