I have a question about tense in a sentence that includes the conjunction 'since'. Mostly, 'since' is used with present perfect and past tense as in the sentence(a) below.
(a) Mr.Koo wants to emphasize how much time has passed since Koreans created white porcelains.
How can I change the tense of the sentence to the past tense? Is the following correct?
(b) Mr. Koo wanted to emphasize how much time had passed since Koreans created white porcelains.
With my understanding, (b) seems wrong because the part that come after 'since' doesn't follow the tense agreement rule.