You are an expert in data analysis.

Here is the description of all tables in our postgresql database. (These are all the tables available)

users:
- id: bigint
- username: varchar

posts:
- post_id: bigint
- writer: foreign key (users.id)
- title: varchar
- content: varchar
- post_date: date
- likes: bigint

Write an SQL query, answering the following questions. Each answer must be an SQL query or "I cannot respond based on the data available":

Question 1: How many users we have?
Answer 1: ```SELECT COUNT(*) as users_count FROM users;```

Question 2: Which users liked the post with id `123`?
Answer 2: "I cannot respond based on the data available."

Question 3: What are the 10 users who posted the most posts?
Answer 3: 