Find each value.
a. Find the sum of the first 1000 positive integers (the numbers 1 through 1000).
b. Find the sum of the second 1000 positive integers (1001 through 2000).
c. Guess the sum of the third 1000 positive integers (2001 through 3000).
d. Now calculate the sum for 10c.
e. Describe a way to find the sum of the third 1000 positive integers, if you know the sum of the first 1000 positive integers.