What does it mean when you have exhausted your unemployment benefits

the first successful, urban blues recording, selling more than 75,000 copies, was made in year 1920.

mamie smith recorded the first commercially successful example of the urban blues,   with the recording of “crazy blues”."crazy blues" was recorded on august 10, 1920, in new york city. within a month of the release of “crazy blues” it had sold 75,000 copies.

you have to put the parentheses like this:

in fact, you have to perform the operation inside parentheses first, and then proceed in order:

answer; experimentation;

answer; customers within the organization