Question: which is the easternmost river of the north bengal plains

title: Geography of West Bengal
text: West Bengal is on the eastern bottleneck of India , stretching from the Himalayas in the north to the Bay of Bengal in the south . It lies between 85 degree 50 minutes and 89 degree 50 minutes east longitude , and 21 degrees 25 minutes and 27 degrees 13 minutes north latitude . The state has a total area of 88,752 square kilometres ( 34,267 sq mi ) . With Bangladesh , which lies on its eastern border , the state forms the ethno - linguistic region of Bengal . To its northeast lie the states of Assam and Sikkim and the country Bhutan , and to its southwest , the state of Orissa . To the west it borders the state of Jharkhand and Bihar , and to the northwest , Nepal . The capital of the state is Kolkata , the third - largest urban agglomeration and the seventh - largest city in India .