Rank the value of $\oint \overrightarrow{\mathrm{B}}.\overrightarrow{\mathrm{dl}}$ for the closed paths shown in figure from the smallest to largest.

We shall use $\oint \overrightarrow{\mathrm{B}}.\overrightarrow{\mathrm{dl}}={\mathrm{\mu }}_0\mathrm{I},$ where I is the net current enclosed by loop.

Net current enclosed by path a is zero.
Net current enclosed by path c is lA.
Net current enclosed by path d is 3A.
Net current enclosed by path b is 5A.