A cylindrical vessel of height $25\; cm$ and diameter $15\; cm$ on the base is filled with sand. This bucket is emptied on the ground and a conical heap of sand is formed. The height of the conical heap is $30 \;cm$,the radius of its base is ____ cm

Question

$(A) \; 47.4\;cm \\(B)\;45.4\;cm \\(C)\;48.4\;cm \\(D)\;50.4\;cm$