Smith Farmers Association represents a large section of the Midwest. Last year the average corn yield produced by the members of the association was normally distributed with an average of 92 bushels per acre (bu/ac) and a standard deviation of 6.5 bu/ac. What is the z-score for a value of 89 bu/ac?

a) -2.17

b) -0.4615

c) 1.0769

d) -0.3228

e) -0.6154