How Do You Calculate the Line Integral of a Magnetic Field Between Two Points?

[aliaze1]

Homework Statement

What is the line integral of B (vector) between points i and f in the figure?

Homework Equations

?
∫B ds = BL ??

The Attempt at a Solution

What equation would I use for this?

 

[dynamicsolo]

Notice that the wire is perpendicular to the "page" with the current running "into the page", that is, away from you. What does the magnetic field around this wire look like? How does ds point relative to the wire? What equation have you learned about that involved a line integral of B ds?