Given following relational schema, write expressions of SQL query/Relational algebra to answer the following queries.

Relational schema of question

1. Product(model, maker, type)

PC(model, speed, ram, hd, price)

Laptop(model, speed, ram, hd, screen, price)

Printer(model, color, type, price)

1. List the models and prices of all Laptop's with the most expensive first.

2. List the model and price of the Laptops with more than 512 KB RAM and faster than 1.60.

3. List all manufacturers who make PCs.

4. List the model and manufacturer of all Laptops costing less than $ 1,000.

5. List the names and models of the manufacturers who make PCs and laptops with speeds greater than 2. 6) Which manufacturers make PCs, but not printers?