Please provide answer as a relational algebra expression.

Consider the following relation schemas. The primary keys are underlined. All attributes are of type string if not indicated otherwise. Use multi-step and multi-line queries to ease the formulation of queries. Use the rename operator to give intermediate query results a name (some textbooks use the equivalent ' ' notation). Aggregate functions as you can find them defined in some textbooks are not allowed, neither in homework assignments nor in exams. [Note: If the location of your answer for a question is not correctly specified in Gradescope, one point will be deducted.] - Customers(cID, name, city, state) - Orders(oID,cID, orderdate, totalcost:integer) - Products(pID, name, category, price:integer) - SellerProducts(sID, pID) - OrderDetails(oID, pID, discount:integer, sID) - Sellers(sID, name, storeName, city) (a) [5 points] Find the names of sellers and the names of the products they sell that have not been sold yet. Display the sellers' names and the names of the products together. (b) [5 points] Find the names of customers who have ordered an iPad (unique product name) more than once. (c) [5 points] Find the names of sellers and their store names that have offered the highest discount on the product iPad (unique product name). (d) [5 points] Find the names of customers who live in Gainesville and have only purchased products from the category named "computer accessory