The lead analyst at an investment firm has recently analyzed the company's 403(b) clients and determined that the annual contribution is approximately normally distributed with a mean equal to $8,800. Further, he has determined that the probability a customer will contribute more than $18,000 is 0.035. Based on this information, what is the standard deviation of contributions to the 403(b) program? The standard deviation is $. (Round to the nearest cent as needed.)