Consider the following template program average which takes in a list of inte- gers and returns their average as a floating point number. Fill in the blanks. 1 let average 1 - 2 let rec sum (1, acc) = match 1 with | [] => 5 | ::xs -> sum (xs) = 2 2 #in 9 (float (sum (1) _))) 1. (float (List.length 1)) 1 13 For blank 1 in line 4, we should write: For blank 2 in line 6, we should write: For blank 3 in line 9, we should write: What is the type of sum