i have a difficulty on understanding the given, i think the way you wrote it is very confusing, but according to my understanding
united states postal service delivers about 2852 pieces of mail each second.
so the number of mails the postal srvices deliver in 6 days is:
n = (2852 mail / second) ( 6 days) ( 24 hrs / 1 day ) ( 60 min / 1 hr ) ( 60 s / 1 min)
n = 1478476800 mails