It's 4. just took it, that's 1000% the right answer. that other person stinks for that non-answer, sorry. hope this helps. ps. if it's not obvious, you figure it out by taking the hypotenuse (120) and putting it over the height (30). 120/30 is pretty simple division.
It is only active at a pH of around 2 because that is around the same pH as the gastric juices in the stomach which is where pepsin is used to break down proteins.
