How to define the function factorial2 so it can calculate factorial like factorial 4=4*3*2*1=24

use Haskell

factorial2 :: Integer ->Integer factorial2 n - accumulate 1 n where accumulate :: Integer -> Integer -> Integer accumulate a n-undefined factorial2 :: Integer ->Integer factorial2 n - accumulate 1 n where accumulate :: Integer -> Integer -> Integer accumulate a n-undefined