Determine the degree of the polynomial $P(x,y)=x^4+2x^2{y}^3+y^6$ and justify how you found it.

Polynomial degree cannot be determined because there are two variables, and degree is only defined for single-variable polynomials

$6$, because the term $y^6$ has the largest sum of exponents among the terms

$4$, because $4$ is the highest single exponent appearing in the expression, and that determines the polynomial's degree

$5$, because $2x^2{y}^3$ contributes the highest combined exponent count when variables are considered together