Additional topics in contract law include contingent contracts (Section 31) dependent on uncertain future events; void agreements (Section 23-30) lacking essential elements or contrary to public policy; and contract enforceability. Contingent contracts become enforceable when contingency occurs or becomes impossible. Void agreements: Against law, public policy (wagering agreements), restraint of trade, marriage conditions, consideration/objects, uncertain terms. Enforceability requires: Valid formation, lawful object, capacity parties, free consent, possible performance. Essential terms: Parties, consideration, subject matter, performance terms must be clear. Conditions precedent and subsequent affect performance obligations. Time of performance: Strict compliance required unless waived; reasonable time if not specified. Examination of case law on impossibility of performance: Doctrine of frustration applies when performance becomes impossible through no fault. For accountants, contract analysis requires checking all elements; understanding unenforceability grounds prevents disputes. Exam tip: When analyzing contract enforceability, systematically check formation elements, object legality, terms clarity, and performance possibility.