What is the portfolio attachment of the Undersecretary appointed at age 48 with a Chinese name of 梁鳳儀?
CREATE TABLE "undersecretaries" (
  "romanised_name" text,
  "chinese_name" text,
  "age_at_appointment" real,
  "foreign_nationality" text,
  "portfolio_attachment" text,
  "govt_salary" text
);
SELECT "portfolio_attachment" FROM "undersecretaries" WHERE "age_at_appointment"=48 AND "chinese_name"='梁鳳儀';