Regional Manager II

The regional sales manager of a large paper corporation is attempting to detect a difference equal to one deal in the average number of deals closed per week by his employees. To check this, he records the number of deals that $36$ random salespeople make on a random week. He finds the variance of the number of deals that the $36$ random salespeople made to be 9. He runs a statistical test with $\alpha=0.05$ to test the null hypothesis $H_0: \mu = 15$ against his alternative hypothesis $H_a: \mu = 16$. What is the probability of a Type II error? Assume simple random sampling, variance homogeneity, and that the number of deals closed is approximately normally distributed.