#### Answer

1. c
2. c
3. a

#### Work Step by Step

In case one, there is a component of the wind that is going against the plane, so the plane must move faster than 500 km/h. Case two also requires a faster velocity, for the wind is blowing the plane east, so it must be faster than 500 km/h to account for the fact that it cannot go in a straight path. In case three, there is a component of the wind going in the direction of the plane, so it does not need to go 500 km/h to get there in the same time.