what is the cpu for the calculator with 28 kb of ram and display size 128×64 pixels 21×8 characters?
CREATE TABLE "table1_11703336_1" (
  "calculator" text,
  "cpu" text,
  "ram" text,
  "display_size" text,
  "programming_languages" text,
  "link_abilities" text,
  "year_released" text,
  "predecessors" text,
  "successors" text
);
SELECT "cpu" FROM "table1_11703336_1" WHERE "ram"='28 KB of RAM' AND "display_size"='128×64 pixels 21×8 characters';