If the materials static$-$budget variance is $$500$ favourable, and the materials flexible budget variance is $$300$ unfavourable, which of the following must be true?

Select one:

a$.$ The materials sales$-$volume variance is $$800$ favourable.

b$.$ The materials sales$-$volume variance is $$200$ unfavourable.

c$.$ The materials sales$-$volume variance is $$800$ unfavourable.

d$.$ The materials sales$-$volume variance is $$200$ favourable.