Answer
Please see the work below.
Work Step by Step
(a) We know that at the equator, the plane is moving in the magnetic field direction and that is why the induced emf is low. When the plane is flying at the latitude of NY then it is moving perpendicular to the field and thus the induced emf is greater.
(b) We know that the best explanation is option (II) -- that is, the induced emf is greater at New York because the vertical component of the Earth's magnetic field is greater there than at the equator.
