SEMEXCO MARKETING CORP. AT ITS PEAK, 1990 The Cinderella story of business magnate Alfredo Yao is one for the books. Left without a father as a child of 13, he managed a stallin the Bluemntritt, Sta. Cruz area selling all sorts of products. At age 17, he put up a printing business, Solemar Commercial Printing, with a Php 3000 loan. ZEST-O, THE COMPANY'S BIGGEST SUCCESS, launched 1980 As his lot improved, he chanced upon a new concept of affordable printed packaging in 1979 while on tour in…