there is two countries A and B, the distance between them is 1200 km.
there is a company in country A wants to transport some goods to country B, so the company decided to hire a number of planes, each plane has a tank with Capacity 60 Liters initially all tanks are full of fuel, one liter of fuel can transport a plane only 10km.
unfortunately, a plane with full tank can fly 600km which is not enough to travel to country B.
a plane can be used to help another plane with fuel , if two planes are in the same point one plane can transfer any number of liters of fuel from its tank to the other plane's tank while they are in air ,take care that all planes must back safety to airport in country A before their tanks is empty, expect one plane should travel to country B.
help the company to find a strategy that transport goods to country B using minimum number of planes since hiring a plane is too expensive.
1- a plane cannot be used more that once so when a plane back to airport in country A cannot be used again.
2- one plane is enough to hold all goods so only one plane should arrive to country B.
3- if plane2 wants to transfer fuel to plane1 , both plane1 and plane2 need to be in the same distance from country A .
4- tank of a plane cannot hold more than 60 liter at any time