About 70% Americans are fully vaccinated (at least two doses) as of August 2022. Among the fully vaccinated, Pfizer vaccine share was 60%, Moderna 40%, and other Covid-19 vaccines 0%. The Moderna vaccine was 76% effective at preventing breakthrough Covid-19 infections, but the Pfizer vaccine was 42% effective. Assume no mixing of Vaccines!

1. What proportion of fully vaccinated Americans by Pfizer had a breakthrough Covid-19 infection? (2points)