1. (6 pts.) consider the following relation: employees(eid: integer, sal: real, age: real, did: integer), where attribute eid is the primary key of the relation. employees is stored as a heap file. there is a hash index on did and also a b -tree index on sal. according to the database catalogs, employees has 50,000 tuples, in 1,000 disk blocks (i.e., each disk block holds 50 employees tuples). attribute sal has values between 30,000 and 100,000; attribute did has 1,000 distinct values in employees. consider a query: