Given this schema: Users(uID, username, joinedTime, city) Posts(pID, uID, postTime, postText) Likes(uID, pID, likeTime) Posts[uID] Users[uID] Likes[uID] Users[uID] Likes[pID] Posts[pID] Solve all queries below using only select (), project (), Cartesian product (), natural join (), and the assignment operator (:=).

Write a query that finds all IDs of posts that have been posted by users in Seattle and liked by users in Portland. This question combines lots of opera- tions; try to break down what you need to do step by step, write the component pieces, and then combine them together.

Answer should be this format.

SNAME(SX(SH(PH=3sP)))