2) Prompt and get the camera’s ISO setting.
The ISO value should be validated for acceptable values:
6, 8, 10, 12, 16, 20, 25, 32, 40, 50, 64, 80, 100,
125, 160, 200, 250, 320, 400, 500, 640, 800, 1000,
1250, 1600, 2000, 2500, 3200, 4000, 5000, 6400
3) Prompt and get the camera’s aperture or f-stop value.
The aperture should be validated for acceptable values:
f1.2, f1.4, f1.8, f2, f2.8, f4, f5.6, f8, f11,
f16, f22, f32
4) Once name, ISO and aperture are known, the exposure time may
be output, and the program then finishes.
The output exposure time should be an acceptable value and
be the closest value from the list below:
1/4000, 1/2000, 1/1000, 1/500, 1/250, 1/125, 1/60, 1/30,
1/15, 1/8, 1/4, 1/2, 1, 2, 4, 8, 15, 30, 60