[7 marks] Reba the robot and Amby the automatic mopper each travel along the surface of the Earth

from Ksar Kaddour, Algeria (at 30 N, 0 E) to Kikorongo, Uganda (at 0 N, 30 E). Reba travels at a constant speed of 10 km/h: first travelling 10 due south, then 10 due east,

then 10 due south, then 10 due east, then 10 due south, then 10 due east. Amby travels at a constant speed of s km/h, first 30 due east, then 30 due south.

Determine the value of s so that the trip takes Amby the exact same amount of time as Reba.