A programmer writes the following C program:extern double pi;

double square$\_$area$($double side$)\{\}$

double square$\_$perimeter$($double side$)\{\}$

double circle$\_$area$($double radius$)\{\}$

double circle$\_$perimeter$($double radius$)\{\}$The geometry. h header declares square$().$

What symbols can be fully resolved at compile time? What symbols does the linker need to resolve?