A large state university is interested in estimating the average monthly earnings of its alumni who graduated with a graduate degree (e.g., MSC, MA, MFA, PhD, etc.) over the last decade. From a large population with 5,305 observations (N=5,305), they select a random sample of 200 observations (n=200). The sample mean is $3,107.25 and the sample standard deviation is $419.78. For simplicity, they consider the confidence level to be equal to 95% and critical value (the t-value) to be equal to 2.

Estimate the unknown population mean using a 95% confidence interval.

Using the WDI package in R, look for the following term: lending interest rate. It is associated with variable name: FR.INR.LEND. Use R to find the median lending interest rate for the United States from 1984 to 2017 . Then, fill out the blank. The median lending interest rate for the US from 1984 to 2017 is about percent. (Enter your answer with two decimal points)