The average height of flowering cherry trees in a certain nursery is 11 feet. if the heights are normally distributed with a standard deviation of 1.6 feet, find the probability that a tree is less than 13 feet tall.
a.0.67
b.0.89
c.0.95
d.0.78

Calculate first the value of the z-score of the given data point in this distribution. 
                                  z-score = (D - m) / s
where D is the data point, m is the mean, and s is the standard deviation. 

Substituting the values,
                                 z-score = (13 - 11) / 1.6 = 1.25
This z-score translates to a percentile of 89%. Thus, the answer is letter B.