Answer:
insouciance- the condition of being unconcerned
lighthearted
worry free / free from worry
Sarah had a very 'insouciant' attitude toward her failed math exam. [She didn't much care about failing the exam.]
Jacob took to the news with much 'insouciance.' [He didn't much care about the news, or what effect it may have.]
If you do not understand, let me know, and I can explian it another way.
You wouldn't notice him much by his insouciant demeanor; But I can assure you that He is a very, very wealthy man.