Customers experiencing technical difficulty with their internet cable service may call an $800$ number for technical support. It takes the technician between $30$ seconds and $13$ minutes to resolve the problem. The distribution of this support time follows the uniform distribution.

b$-2.$ What is the standard deviation of the time? $($Do not round your intermediate calculations. Round your answer to $2$ decimal places$)$

c$.$ What percent of the problems take more than $5$ minutes to resolve? $($Do not round your intermediate calculations, Round your answer to $2$ decimal places$)$

d$.$Suppose we wish to find the middle $50\%$ of the problem$-$solving times. What are the end points of these two times? $($Do not round your intermediate calculations, Round your answer to $3$ decimal places$)$