\text { cet } a, b, c, d \text { be the roots of the polynomial } P(x)=x^{4}+2020 x+2021 . \text { Evaluate the sum } \frac{a^{2}}{a^{3}+2020} \frac{b^{2}}{b^{3}+2020}+ \frac{c^{2}}{c^{3}+2020} \frac{d^{2}}{d^{3}+2020}