Hudson, Inc. is a calendar$-$year corporation. Its financial statements for the years $2021$ and $2020$ contained errors as follows:

$20212020$

Ending inventory $$9,000$ overstated $$24,000$ overstated

Depreciation expense $$6,000$ understated $$18,000$ overstated

$93.$ Assume that no correcting entries were made at December $31,2020.$ Ignoring income taxes, by how much will retained earnings at December $31,2021$ be overstated or understated?

a$.$ $ $3,000$ understated

b$.$ $$22,500$ overstated

c$.$ $$22,500$ understated

d$.$ $$27,000$ understated