Which of the following notations in an E-R diagram means that the entity is optional and a relationship need not have an entity of that type?

Mary has a life estate and her daughter has been named remainderman. Mary leases the property to Susan for 5 years. One year later, Mary dies. Mary's daughter serves notice on Susan to vacate the property. Which of the following is correct?

a. the lease is valid for four more years because it is Susan's private property b. the lease was valid from the beginning because the tenant did not commit waste c. the lease was valid only during Mary's lifetime because it was one of the sticks in the bundle d. the lease was invalid because it violates the statue of frauds

Slack is the amount of time an activity can be delayed without delaying the project

Indicate whether this statement is true or false.