I have 3 questions:
a) What question rating level on CodeForces should I comfortably solve in order to most likely pass Bronze. (Not the actual contest rating on CF but the question rating level)
b) Same as question a) but rating level on CF should I comfortably solve in order to most likely pass USACO Silver.
c) I am aiming to pass USACO Bronze this January. If I have finished solving every Bronze question on USACO is practicing more on random CodeForces questions effective? If not what preparation strategy is the most effective?