William, a baker, claims that his bread height is more than 13 cm, on average. Several of his customers do not believe him, so he decides to do a hypothesis test, at a 5% significance level, to persuade them. He bakes 17 loaves of bread. The mean height of the sample loaves is 13.9 cm. William knows from experience that the standard deviation for his bread height is 0.7 cm. H0: μ≤13; Ha: μ>13 α=0.05 (significance level) What is the test statistic (z-score) of this one-mean hypothesis test?