It should be 75000. I don’t know. I looked this up but I still hope this helps!
Prime factor is a factor that is a prime number.
Prime factors of :
8 : 2 × 2 × 2. Also can be written as

12 : 2 × 2 × 3. Also can be written as

20 : 2 × 2 × 5. Also can be written as

30 : 2 × 3 × 5
56 : 2 × 2 × 2 ×7. Also can be written as

70 : 2 × 5 × 7
You can find all of them by using Factor Tree [ as shown in the picture] or Dividing by prime numbers.
Average rate of change over [1,5] = f(5) - f(1) / 5 - 1
= [(17-5^2) - (17-1) ] / 4
= (-8 - 16) / 4 = -24 / 4 = -6 Answer