A camera takes a absolutely exposed picture if the lens diaphragm is set to f/4 and the shutter speed is 1/250 s.
When the diaphragm is altered to f/11, what must the new shutter speed be so that the exposure is still right? (Standard camera shutter speeds comprise 1/250s, 1/125s, 1/60 s, 1/30s, and 1/15s).