<prompt> Translate the following text to EnglishSasa tuangalie safu za 1 na 2 za Volume ambazo zinaonyesha idadi ya vipande vya barua za darasa la kwanza kwa kila sekta kwa miaka ya kifedha ya 1987, 1990, 1993, na 1997.  <response>: Now let us turn to columns in Table 1. Columns 1, 3, 6, and 9, labeled Volume show, in millions, the total First-Class Mail pieces broken-down by sector for FYs 1987, 1990, 1993 and 1997, respectively. 