Using F#, given function is sum_some : int option list -> int:

let rec sum_some xs = match xs with | None::xs -> sum_some xs | Some x::xs -> x + sum_some xs | [] -> 0

Rewrite the following function using:

a) List.fold by filling in the ... in

let sum_some2 xs =
	List.fold (fun s o ->
		match o with
		...) 0 xs

b) List.fold and List.map by filling in the ... in

let sum_some3 xs =
	Let f o = ...
	List.fold (+) 0 (List.map f xs)