pls tell all a,b and c part. pls explain in bit detail.

3. Suppose the borders of a state, B, coincide with the circumference of a circle of radius r > 0, and its population is distributed uniformly within its borders (so that the proportion of the population living within some region of B is simply the proportion of the state's total land mass contained in that region), with total population normalized to 1.For any resident of B, the cost of travelling a distance d is kd, with k> 0.Every resident of B is endowed with an income of 10, and is willing to spend up to this amount to consume one unit of a good, G, which is imported from outside the state at zero transport cost. The Finance Minister of B has imposed an entry tax at the rate 100% on shipments of G brought into B. Thus, a unit of G costs p(1+1) inside the borders of B, but can be purchased for just p outside; p(1+1) 0, and its population is distributed uniformly within its borders (so that the proportion of the population living within some region of B is simply the proportion of the state's total land mass contained in that region), with total population normalized to 1.For any resident of B, the cost of travelling a distance d is kd, with k> 0.Every resident of B is endowed with an income of 10, and is willing to spend up to this amount to consume one unit of a good, G, which is imported from outside the state at zero transport cost. The Finance Minister of B has imposed an entry tax at the rate 100% on shipments of G brought into B. Thus, a unit of G costs p(1+1) inside the borders of B, but can be purchased for just p outside; p(1+1)