The phrase "am concerned with" is spelled with the letter "c" instead of "s" because it is a combination of the verb "concern" and the preposition "with". In IPA phonetic transcription, it sounds like /əm kənˈsɜrnd wɪð/. The "c" makes a "k" sound before the vowel "e" in "concern", while the "s" in "am" makes a "z" sound before the consonant "c" in "concerned". The "w" in "with" is pronounced as /w/, making a separate syllable.