SASMO 2020 Grade 6 Question 1

Platform scoring: start at 0; Q1–15: 2 points each; Q16–25: 4 each; wrong or blank: 0; maximum 70. Official SASMO reference scoring is separate: start at 15, Section A +2/−1/0 and Section B +4/0/0 for correct/wrong/blank, maximum 85.

Find the value of $2020\times2020-2019\times2021$.