Contracts That Must Be in Writing 必須以書面訂立的合同

I agree to mow your lawn. You agree to pay me $25. I mow your lawn you give me $15. I threaten to sue.我同意替你刈(yi)草坪。你答應付給我25美元。我刈了你的草坪。你給了15美元。我以起訴要挾。