The error is in part (A) "Can I join you" - this is an inappropriate modal usage in the given context. The phrase "and contribute my mite" suggests a serious, professional context (contributing to a delayed project). In such contexts, "May I join you" or "Could I join you" would be more appropriate and polite. "Can I" is more casual and emphasizes capability rather than seeking permission, which doesn't fit the formal tone of the rest of the sentence.