From a solid cylinder of height 2.8 cm and diameter 4.2 cm, a conical cavity of the same height and same diameter is hollowed out. Find the total surface area of the remaining solid. 
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Slant height of the cone, l = 
Remaining area of the cylinder = Curved surface area of the cylindrical part + Area of the conical part + Area of cylindrical base
= 2πrh + πrl + πr2
= 2π × (2.1)× (2.8) + π × 2.1 × (3.5) + π (2.1)2
= 36.96 + 23.1 + 13.86
= 73.92 cm2
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