Riya checks her fitness band after her morning walk. It shows four readings: the distance she walked, $2.4\ \text{km}$; the time she took, $30\ \text{min}$; the energy she used, $150\ \text{kcal}$; and how far she now is from home, $1.1\ \text{km}$ towards the north-east. Which of these readings is a vector?