Standard Deviation about Median

Q. Standard deviation for n observations $x_1,x_2\dots x_n$ is '5' then the standard deviation of n observations $5x_1,5x_2,\dots 5x_n$ will be ___

Q. Standard deviation for n observations $x_1,x_2,\dots x_n$ is 5, then the standard deviation for n observations $x_1+1,x_2+1,\dots x_{n+1}$ will be ___

Q. Find the standard deviation for the following data:
$\begin{array}{cccccc}{x}_i& 3& 8& 13& 18& 23\\ f_i& 7& 10& 15& 10& 6\end{array}$

1. 15.92
2. 6.12
3. 13.87
4. 5.37