A college has 220 full-time employees that are currently covered under theschool's health care plan. The averageout-of-pocket cost for the employees on the plan is $1,940 with a standard deviation of $520. The college is performing an audit of its health care plan and has randomly selected 30 employees to analyze theirout-of-pocket costs.

a. Calculate the standard error of the mean.

b. What is the probability that the sample mean will be less than $1,885?

c. What is the probability that the sample mean will be more than $1,905?

d. What is the probability that the sample mean will be between $1,965 and $1,990?

a. The standard error of the mean is

.