Answer:
For example, in the table showing the demand and supply schedule for T shirt at different prices (see file attached), the equilibrium price for a unit of T shirt is $3, at equilibrium, QD = QS (i.e. 30 = 30).
A shortage is recorded when the price of T shirt falls below equilibrium price of $3 as shortage of T shirt is recorded, i.e. @ $2, QD>QS (40>20). A shortage of 20 is recorded.
Surplus occurs as price increases above equilibrium price of which QD<QD, i.e. @ $4, a surplus of 20 is recorded.