A 4 m thick soft clay layer with the degree of consolidation of 58% is sandwiched between layers of sand. The initial effective overburden pressure at the middle of the clay layer before the construction is 260 kPa, and the permanent pressure on the clay is expected to increase by 125 kPa from a building structure construction on ground. Determine the extra surcharge needed to eliminate the entire primary consolidation settlement for the clay layer: 1) without vertical drains 2) with vertical drains if r = 0.15 m and d = 3 m, C, C, = 0.30 m²/month