婉謝邀請信函

Dear Sirs，My wife and I were very grateful to receive an invitation to attend the celebrations marking the opening of your new factory．We are sorry to inform you that we have to decline your invitation owing to a previous engagement．Yours faithfully，中文對照敬啟者：我和夫人非常感謝閣下邀請參加貴公司新建工廠開業典禮慶祝儀式。但由於事先有約，無法應邀前來參加，深表遺憾。×××敬上