Influx of which ion through the T-tubules will cause calcium release from the sarcoplasmic reticulum?

Skeletal muscle fibers are made up of white and red fibers. White fibers are considered fast-twitch and red fibers are considered slow-twitch.

Which of these statements INCORRECTLY describes a difference between white and red fibers?

The triceps brachii extends the arm, while the biceps brachii flexes the arm. How is the biceps brachii related to the triceps brachii?