Slant height of the cone, l = \(\sqrt{(2.8)^2 + (2.1)^2}\) = 3.5 cm

Remaining area of the cylinder = Curved surface area of the cylindrical part + Area of the conical part + Area of cylindrical base

= 2πrh + πrl + πr^{2 }

= 2π × (2.1)× (2.8) + π × 2.1 × (3.5) + π (2.1)^{2}

= 36.96 + 23.1 + 13.86

= 73.92 cm^{2}