Find $\oint \overrightarrow{B}·\overrightarrow{dl}$ over following loops (direction in which integration has to be performed is indicated by arrows)

Two infinite sheets of current are carrying current $\lambda$ per unit length as shown in figure. Find magnetic field at points $A, B$ and $C.$

A solid thin wire is located inside two $co$-axial long cylindrical shells, each carrying current $i$ as shown in figure. Assuming wires to be infinitely long, find magnetic field at a point which is at a distance $x$ from the axis. Assume that $a<x<b.$

Find magnitude and direction of force on following current carrying wires. Direction of magnetic field has been indicated in each case.