Given the following two tables, express in Relational Algebra the queries below: PC (model, speed, ram, hard_disk, price) Laptop (model, speed, ram, hard_disk, price) a) List the models of PCs that have a speed of at least 3.00. [1 mark] b) List the details of laptops having hard disk capacity less than 1000 and price greater than 500 OMR. [1 mark] c) List all the available models of PCs and Laptops. [1 mark]