D and E are points on the sides AB and AC respectively of ΔABC. In which of the following cases DE ∥ BC?

1. AD = 3 cm, BD = 8 cm, AC = 8 cm, AE = 3 cm

2. AD = 5 cm, BD = 6 cm, AE = 6 cm, CE = 5 cm

3. AB = 18 cm, AD = 8 cm, AE = 12 cm, EC = 15 cm

4. none of these