Inner radius (r) of circular well = (3.5/2)m = 1.75m

Depth (h) of circular well = 10 m

Inner curved surface area = 2πrh

= (2 x 22/7 x 1.75 x 10) m^{2}

= (44 x 0.25 x 10) m^{2}

= 110 m^{2}

Therefore, the inner curved surface area of the circular well is 110 m^{2}.

Cost of plastering 1 m^{2} area = Rs 40

Cost of plastering 100 m^{2} area = Rs (110 × 40) = Rs 4400

Therefore, the cost of plastering the CSA of this well is Rs 4400.