Cost or Costs?
I'm studying with a book and in one exercise it has the following phrase as an answer:
"It cost twelve pounds to have my suit cleaned"
And the answer I thought was the correct one is:
"It costs twelve pounds to have my suit cleaned"
So, my question is, when do I have to use this "s" at the end? I always thought that everytime I use "it" I should use costs, because of simple conjugation (I/You/They cost; He/She/It costs).. Am I right or Am I missing something?