for how many years did hallgrimur sveinsson serve as the bishop of iceland ?
CREATE TABLE table_203_875 (
    id number,
    "#" number,
    "name" text,
    "birth and death" text,
    "office started" text,
    "office ended" text
)
SELECT "office ended" - "office started" FROM table_203_875 WHERE "name" = 'hallgrimur sveinsson'
Below are sql tables schemas paired with instruction that describes a task. Using valid SQLite, write a response that appropriately completes the request for the provided tables. ### Instruction: for how many years did hallgrimur sveinsson serve as the bishop of iceland ? ### Input: CREATE TABLE table_203_875 (
    id number,
    "#" number,
    "name" text,
    "birth and death" text,
    "office started" text,
    "office ended" text
) ### Response: SELECT "office ended" - "office started" FROM table_203_875 WHERE "name" = 'hallgrimur sveinsson'