(used to express one's emphatic agreement with the interlocutor's statement or affirmative response to a question) definitely, certainly: (but) of course!
naturally!what do you think!you said it!I'll say!
«Это ведь настоящий мех?» - «Я думаю! Посмотри на цену!» "This is real fur, isn't it?" "But of course! Look at the price!"