What is the total surface area of this figure?
What is the definition of "surface area"? Please answer me in Chinese.
I will give the person 10 marks if he/she answers the most detail.
更新1:
Actually, I want to know that do we also need to calculate the grey area?
更新2:
Sorry, I think that there are some people answer quite well. I can't decide which one is the best one. Therefore, I give a chance to people to vote for you all!