So, it is likely such a Roman prefix has from one to four letters.
the derived probabilities embody a number of relationships: (a) Phoneme to syllable relationships (e.g., "b" vs. " 布 " as in "Brooklyn" and " 布 魯 克 林"(Bulukelin)), (b) Syllable to syllable relationships (e.g., "bu" vs. "布"), (c) Phonics rules (e.g., "br-" vs. "布" and "克" vs. "cl-").