The longest side of a triangle is three times the shortest side and third side is $2\;cm$ shortest than the longest side. If the perimeter of the triangle is at least $61\; cm$ find the minimum length of the shortest side.

Question

$\begin{array}{1 1} (A)\;9\;cm \\(B)\;3\;cm \\(C)\;5\;cm \\(D)\;5\;cm \end{array}$