$$V = \int \left(\vec{v} \times \vec{B}\right) \bullet \vec{dl} - \int _S \frac{\vec{dB}}{dt} \bullet \vec{ds}$$
From the statement I know that: B⊥v, (B x v) // dl and B // ds.
$$V = \int vBdl - \oint _S \frac{dB}{dt} ds$$
v is the speed with which all the segments dl are aproximating to the...