CREATE TABLE table_17130 ("Calculator" TEXT, "CPU" TEXT, "RAM" TEXT, "Display Size" TEXT, "Programming Languages" TEXT, "Link Abilities" TEXT, "Year Released" TEXT, "Predecessors" TEXT, "Successors" TEXT)

what is the cpu for the calculator with 28 kb of ram and display size 128 64 pixels 21 8 characters?
SELECT "CPU" FROM table_17130 WHERE "RAM" = '28 KB of RAM' AND "Display Size" = '128×64 pixels 21×8 characters'
SELECT "CPU" FROM "table_17130" WHERE "Display Size" = '128×64 pixels 21×8 characters' AND "RAM" = '28 KB of RAM'