$2.$ Use the built$-$in function 'rand' to generate $\backslash (1\backslash$times $100\backslash )$ random vector $\backslash ($ v $\backslash ).$ Then make your own programming codes to solve the following problems $($do not use built$-$in functions$)$ :

$(1)$ find the maximum and minimum values.

$(2)$ find a number closest to $0\mathrm{.}4.$

$(3)$ find how many components of the vector are between $0\mathrm{.}2$ and $0\mathrm{.}5.$

$(4)$ rearrange the vector $\backslash ($ v $\backslash )$ in the decreasing order.