Two long fixed parallel wires, A and B, are 10 cm apart in air and carry 40 A and 20 A, respectively, in opposite directions. Determine the resultant field 

(a) On a line midway between the wires and parallel to them and 

(b) On a line 8.0 cm from wire A and 18 cm from wire B. 

(c) What is the force per meter on a third long wire, midway between A and B and in their plane, when it carries a current of 5.0 A in the same direction as the current in A?