The amount of the adjustment to record the estimate of sales returns at the end of an accounting period is calcualted by

a$.$ Using an estimate of returns expected from this period's sales and subtracting any actual customer returns during the period after the

prior period estimate is zeroed.

b$.$ Using an estimate of returns expected from this period's sales and subtracting all actual customer returns during the period

c$.$ The amount estimated in the prior period

d$.$ None of the above.