f/16 at 1/125 second
The "rule" is called "Sunny-16" and the idea is the f/stop is f/16
Then the shutter speed is 1/ the ISO or rated speed of the film
In my case I rate 400 speed film at 250 for landscapes and so my case I use f/16 at 1/250 second
In your case, I assume you were using a slow, fine-grain film that might be 100 speed so you could use f/16 at 1/125 second
You could, if you are using 100 speed film, choose to expose it as if it were 64 speed, and give f/16 at 1/60 second
For landscape in black and white it would be good.