write a method named firstpluslast that will take an array of integers and return the sum of the first and last integers. for example, if the first integer in the array is 3 and the last integer is 5, then it should return 8. if the array only contains one element (e.g., 7), then the first and last integer in that array is the same (so for 7, it should return 14). if the array is empty, it should return 0.