According to credit reporting agency Experian, the population of consumer credit card holders carries an average credit card balance of $5500, with a standard deviation of $750. You plan to draw a random sample of 625 credit card holders from this population. 

a. What is the probability that the average credit card balance for the sample will be somewhere between $5450 and $5550? 

b. How likely is it that the average balance in the sample will be within ± 1 standard deviation (that is, ±1σ_x-bar) of the population average within ± 2 standard deviations? 

c. It is 95% likely that the sample average will be within ± $____ of the population average.