1. Specify relational calculus expression for the following descriptions on the database schema shown in Figure 3.5 using the relational operators discussed in this chapter. Also, show the result of each query if applied to the database of Figure 5.7 (pg. 164). a. Retrieve the names of employees in department 5 who work more than 10 hours per week on the 'ProductX' project. b. List the last names of department managers who have no dependents.