Find sum of all numbers in file

Given a file which contains integer values. Find the sum of all integer numbers.

Write a function: def solution(FN):

that accepts a file name. The function should find the sum of all the numbers in a file and return the sum.

Input 1 2 3 4 5 4 5 6 73 4 1

Note: File contains numbers separated by single or multiple spaces.

Output 108