虽然工程师们无法确定新计划是否奏效，但至少书面上看来是个解决问题的好方案。关键词汇：certain：确定；solution：解决方案。难点在于第一个句子从句的理解，如果能把work这个词翻译好的话，这句话也就能理解了。

We had a great time yesterday. We went to the Darling Harbor where we had lunch, and then we drove around Sydney and saw a bit of the city.

Although the engineers could not be certain that the new plan would work, it seemed like a good solution to the problem, at least on paper.