Draw the ER diagram using an ISA relationship for the following example:

Assume in a company, we have two kinds of staff, namely salaried$-$employees and contract$-$employees. Both have a unique identifier SSN and a name. For salaried$-$employees we keep track of their yearly salary as well as the department to which they have been assigned to$.$ For contract$-$employees, we keep track of the number of hours they have a contract for, the hourly rate of pay, as well as the project number for the project in charge of this contract.