Could somebody help me 'total differentiate' this question please?

K = 12x^3y + 10x^2y^2 + 6xy^3 +4y^4

I don't really know where to begin this is what i have down

fx = 36x^2 y + 20xy^2 + 6y^3 +4y^4

fy = 12x^3 + 10x^2(2y) + 6x(3y^2) + 16y^3

then im lost on the total differential formula

DK = dk/dx (DK) + dk/dy (DY)

(where the small 'd' represents the differential symbol

am i completely lost?