Please answer a question about the following article about Punjab, Pakistan:

Punjab's geography mostly consists of the alluvial plain of the Indus River and its four major tributaries in Pakistan, the Jhelum, Chenab, Ravi, and Sutlej rivers. There are several mountainous regions, including the Sulaiman Mountains in the southwest part of the province, and Margalla Hills, Salt Range, and Pothohar Plateau in the north. Agriculture is the chief source of income and employment in Punjab; wheat and cotton are the principal crops. Since independence, Punjab has become the seat of political and economic power; it remains the most industrialised province of Pakistan. It counts for 39.2% of large scale manufacturing and 70% of small scale manufacturing in the country. Its capital Lahore is a major regional cultural, historical, and economic centre.

What plain is Punjab in?
the alluvial plain of the Indus River