Answer:
Step-by-step explanation:
CI ( 95 % )  means  α = 5 %   α  = 0,05  α /2 = 0,025
If we have a normal distribution and build a CI by symmetry such CI has as a middle point the mean in this case
CI 95 % Â = Â ( 520 ; Â 560 )
the mean is (520 + 560 ) / 2 Â
mean  = 540