How many distinct 7-letter arrangements can be formed from the letters of the word 'INCONCEIVABLE' (without using any letter more times than it appears in the word) such that the letters in the odd positions (1^st, 3^rd, 5^th, 7^th) are chosen from the letters that appear exactly once in the word, and the letters in the even positions (2^nd, 4^th, 6^th) are chosen from the letters that appear exactly twice in the word?