In a certain code, 'book is big' is written as 756; 'big is story' is 764 and 'story book is interesting' is 4356. Which digit represents 'interesting'?
A plane flies 100 km West, then it turns South and flies 150 km, then it turns West and flies 300 km, then it turns to its right and flies 150 km. Where is it now with reference to its starting position?