model from them.

A key may open multiple doors.

A door may be opened by more than one key.

a$.$ What entities would you add to the data model? $($For full credit, follow conventions.$)$

KEY, DOOR

b$.$ What relationship$($s$)$ would you add to the data model? For each relationship, state its connectivity. $($In other words, is it one$-$to$-$one, one$-$to$-$many, or many$-$to$-$many?$)$