Help Please

Imagine you are conducting an analysis on the amount that consumers will pay for the inclusion of a wireless charging feature on a new cell phone. After sampling 30 people, you create a confidence interval around the mean, and find the upper bound to be $76.67, while the lower bound was $56.89. You used a confidence level of 95%. Using this information, what was standard error of the sample average you used in your analysis? Note: 1- Only round your final answer. Round your final answer to two decimal places