Assume that you are a graduate and with few of your friends, you have founded a startup company where you are the database designer. Since ride sharing service-based apps are really doing good and the rainy season is knocking at the door, your creative team has come up with an app idea, named BHASHAO. The business logic of BHASHAO is quite similar to other ride sharing apps, however, your app is unique since this will deal with boat sharing. Anyhow, you have started your database design where the DB is named as 'bhashaoDB'. You have initially identified the necessity to store the following information: For the app user (rider), you need to store name, NID, cell number, address and one emergency contact number. For the boat, its id, start location, end location, capacity and fee. For the boat owners, their name, NIDs, and district. A boat owner may have multiple boats; however, each boat is operated by exactly one owner. And For every trip, store the riders in the trip, the boatman who sailed, fee paid by each rider. A trip may have multiple riders, and a boatman may be working with multiple boat owners.

Question:

Produce the SQL and relational algebra to show NID of all the rider who have travelled by those boats which are owned by any resident from Dhaka.