The time to check out and process payment information at an office supplies Web site can be modeled as a random variable with mean \(\mu=63\) seconds and variance \(\sigma^{2}=81\). If the sample mean \(\bar{X}\) will be based on a random sample of \(n=36\) times, what can we assert about the probability of getting a sample mean greater than 66.75, if we use

(a) Chebyshev's theorem;

(b) the central limit theorem?