The solution would be like this for this specific problem:
7 x 30 = 210
210 + 55(2) = 320
The surface area of the prism is 320 mm2.
The correct answer between all the choices given is the second choice or letter B. I am hoping that this answer has satisfied your query and it will be able to help you in your endeavor, and if you would like, feel free to ask another question.