Help me with this question​

Check all that apply. f is a function. f is a one-to-one function. c is a function. c is a one-to-one function.

If u good at math hit me up on insta or sum @basic_jaiden or @ and

Fatima plans to spend at least $15 and at most $20 dollars on sketch pads and pencils. if she buys 2 sketchpads, how many pemcils can she buy while staying in her price range? fatima can buy between and pencils. ? (type whole numbers. use ascending? order.)