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We know that Sum of first n odd numbers is n square. Sum of first n even numbers is n(n+1). Sum of first n natural numbers is n(n+1)/2. Thus sum of first n 2000 even numbers is 2000(2000+1)=4002000. And sum of first n odd numbers is 2000 square=4000000. Hence 4002000-4000000=2000. Now sum of first 100 whole numbers = sum of first 99 natural numbers. That is 99 (99+1)÷2=4950. Hence 4950×2000=9900000.

The sum of first $n$ even numbers - The sum of first $n$ odd numbers = $$ (Always)

$\text{The sum of first 100 integers = sum of first 99 natural numbers }$

That is equal to $\large \frac{99 \times 100}{2}$

$\text{The required answer = }\large \frac{99 \times 100}{2} \times 2000$

$\text{ Which is equal to } 99 \times 100 \times 1000 = \boxed{9900000}$