A certain type of film requires an exposure time of 0.011 s with an f/11 lens setting. Another type of film requires twice the light energy to produce the same level of exposure. What f- stop does the second type of film need with the 0.011 s exposure time? (Com mon f- stops are 1, 1.2, 1.4, 1.8, 2, 4, 8, 11)