joseph, he should betray the other guy.
If he is silent he will either get 6 months (if the other guy is also silent) or 10 years (if his friend betrays him).
If he betrays his friend, his minimum goes down to no jail time (if the other guy is silent) and his maximum goes down to 5 years (if the other guy betrays).
so his choice is to have a range of 6 months to 10 years or to have a range of zero to 5 years.
But boy is that prosecutor unfair, lol.