You have just been employed by the ROBCOR Trucking Company to develop a database. To gain a sense of the database’s intended functions, you have spent some time talking to ROBCOR’s employees and you’ve examined some of the forms used to track driver assignments and truck maintenance. Your notes include the following observations:

• Some drivers are qualified to drive more than one type of truck operated by ROBCOR. A driver may, therefore, be assigned to drive more than one truck type during some period of time. ROBCOR operates several trucks of a given type. For example, ROBCOR operates two panel trucks, four half-ton pick-up trucks, two single-axle dump trucks, one double-axle truck, and one 16-wheel truck. A driver with a chauffeur’s license is qualified to drive only a panel truck and a half-ton pick-up truck and, thus, may be assigned to drive any one of six trucks. A driver with a commercial license with an appropriate heavy equipment endorsement may be assigned to drive any of the nine trucks in the ROBCOR fleet. Each time a driver is assigned to drive a truck, an entry is made in a log containing the employee number, the truck identification, and the sign-out (departure) date. Upon the driver’s return, the log is updated to include the sign-in (return) date and the number of driver duty hours.

• If trucks require maintenance, a maintenance log is filled out. The maintenance log includes the date on which the truck was received by the maintenance crew. The truck cannot be released for service until the maintenance log release date has been entered and the log has been signed off by an inspector.

• All inspectors are qualified mechanics, but not all mechanics are qualified inspectors.

• Once the maintenance log entry has been made, the maintenance log number is transferred to a service log in which all service log transactions are entered. A single maintenance log entry can give rise to multiple service log entries. For example, a truck might need an oil change as well as a fuel injector replacement, a brake adjustment, and a fender repair.

• Each service log entry is signed off by the mechanic who performed the work. To track the maintenance costs for each truck, the service log entries include the parts used and the time spent to install the part or to perform the service. (Not all service transactions involve parts. For example, adjusting a throttle linkage does not require the use of a part.)

• All employees are automatically covered by a standard health insurance policy. However, ROBCOR’s benefits include optional co-paid term life insurance and disability insurance. Employees may select both options, one option, or no options.

Given those brief notes, create the ER diagram. Make sure you include all appropriate entities and relationships, and define all connectivities and cardinalities.