Total cost of fencing the circular field = Rs. 2640

Cost per metre fencing = Rs 12

Total cost of fencing = circumference x cost per fencing

⇒ 2640 = circumference x 12

⇒ circumference = 2640/12=220m

Let radius of field be r m

Circumference = 2πr m

2πr = 220

2 x 22/7 x r = 220

r = 70/2=35m

Area of field = πr^{2}

= 22/7x35x35

= 3850 m^{2}.

Cost of ploughing per m^{2} land = Rs. 0.50

Cost of ploughing 3850 m^{2} land = 1/2 x 3850

= Rs. 1925.