The white dwarf that remains when our sun dies will be mostly made of

Carbon and oxygen

Explanation:

White dwarfs are the stars which have used all their hydrogen and helium fuel and now exists with only carbon and oxygen in their core. Their size reduces up to one hundredth times of the size of their sun in early stages and yet they possess the same mass.  

Due to loss of fuels and impact of gravity, a young star collapses on itself leading to formation of dwarf star.

see the picture for the vector

the magnitude of the vector by pythagorean theorem

r = √( (-10)^2 + (3)^2 ) = √109

magnitude = √109 units

the direction angle between vector and x-axis is

tan^(-1)(3/10) = 16.699

so the direction is approximately 16.7 degrees north of west