CREATE TABLE table_29156 ("No. in series" FLOAT, "No. in season" FLOAT, "Title" TEXT, "Directed by" TEXT, "Written by" TEXT, "Original air date" TEXT, "U.S. viewers  ( million ) " TEXT)

How many viewers in millions did the Alison McDonald episode get?
SELECT "U.S. viewers (million)" FROM table_29156 WHERE "Written by" = 'Alison McDonald'
SELECT "U.S. viewers (million)" FROM "table_29156" WHERE "Written by" = 'Alison McDonald'