Carla wants to buy Ben's house for $221.000. Carla includes a contingency clause in the offer stating that she must sell her current house first. Ben agrees as long as Carla's house sells within 45 days. They sign the purchase agreement. During the 45 day period, the contract is:
a. Executed.
b. Executory.
c. Voldable.
d. Unenforceable.