Otlavis and Ferdland are two southern states in the country of Blendland that share a common border. They share water from Lake Clarly, and therefore, sign an agreement pledging the protection of the lake and its premises in order to sustainably use its water. Which of the following types of agreements is signed by the two states mentioned in the scenario?​
a. ​Block contract
b. ​Unfunded mandate
c. ​Interstate compactd. Mayflower compact​
e. ​Federal mandate