how many times is 90v listed as the electrical system ?
CREATE TABLE table_204_131 (
    id number,
    "tops design code" text,
    "electrical system" text,
    "max speed" text,
    "weight" text,
    "brakes" text,
    "route availability" number,
    "notes" text
)
SELECT COUNT(*) FROM table_204_131 WHERE "electrical system" = '90 v'
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: how many times is 90v listed as the electrical system ? ### Input: CREATE TABLE table_204_131 (
    id number,
    "tops design code" text,
    "electrical system" text,
    "max speed" text,
    "weight" text,
    "brakes" text,
    "route availability" number,
    "notes" text
) ### Response: SELECT COUNT(*) FROM table_204_131 WHERE "electrical system" = '90 v'