Draw an ER diagram addressing following rules:
A small maintenance company has asked you to make a database to manage the task assignments on a work order. A work order records the set of tasks requested by a customer at a specific location. A customer has a name, address and collection of submitted work orders. A work order has a number, create date, date required, completion date, optional supervising employee, work address and a set of tasks. Each task has a number, task name, hourly rate and estimated hours. Tasks are standardized across work orders so that the same task can be performed on many work orders. Each task on a work order has a status (not started, in progress, or completed), actual hours and a complete date. The estimated number of hours for a task depends on the work order and task, not on the task alone; therefore, each task of a work order includes an estimated number of hours. The completion date is not entered until the status changes to complete. The company wants to maintain a list of materials. The data about materials include a material number, name and unit cost. Each work order also has a collection of material requirements. A material requirement includes a material, an estimated quantity of the material, and the actual quantity of the material used.