Part 1. The probability of choosing the letter A is 2/18, which simplifies to 1/9. Therefore, the probability is 0.111.
Part 2. There are 13 consonants out of 18 letters. So the probability of choosing a consonant is 13/18. Therefore, the probability is 0.722.
Part 3. The word "of" contains the letters o and f, which are both present in the sign. Therefore, the probability of choosing a letter from the word "of" is 2/18, which simplifies to 1/9. Therefore, the probability is 0.111.