Both statements are correct based on the geography and climatology of India. Firstly, the duration of the monsoon is longer in southern India due to its proximity to the Indian Ocean, which influences the southwest monsoon's arrival and sustenance, whereas northern India experiences a shorter monsoon season as it is farther from this moisture source. Secondly, in the northern plains, the amount of annual rainfall decreases from east to west due to the orographic effect of the Himalayas, which block the moisture-laden winds from moving further inland, resulting in higher rainfall in the east (like in West Bengal) and progressively lower amounts as one moves westward towards Punjab and Rajasthan. This understanding is crucial in analyzing India's agricultural patterns and water resource management, topics relevant for the UPSC examination.