#### S1

From point \(B\) to point \(C\), price rises from \(\$70\) to \(\$80\), and \(Q_d\) decreases from \(2,800\) to \(2,600\). So:

\[\begin{align*} \% \text{ change in quantity} &= \frac{2600-2800}{(2600+2800)\div 2}\times 100\\ &= \frac{-200}{2700}\times 100\\ &= -7.41 \end{align*}\]

\[\begin{align*} \% \text{ change in price} &= \frac{80-70}{(80+70)\div 2}\times 100\\ &= \frac{10}{75}\times 100\\ &= 13.33 \end{align*}\]

\[\begin{align*} \text{Elasticity of Demand} &= \frac{-7.41\%}{13.33\%}\\ &= 0.56 \end{align*}\]

The demand curve is inelastic in this area; that is, its elasticity value is less than one.

Answer from Point \(D\) to point \(E\):

\[\begin{align*} \% \text{ change in quantity} &= \frac{2200-2400}{(2200+2400)\div 2}\times 100\\ &= \frac{-200}{2300}\times 100\\ &= -8.7 \end{align*}\]

\[\begin{align*} \% \text{ change in price} &= \frac{100-90}{(100+90)\div 2}\times 100\\ &= \frac{10}{95}\times 100\\ &= 10.53 \end{align*}\]

\[\begin{align*} \text{Elasticity of Demand} &= \frac{-8.7\%}{10.53\%}\\ &= 0.83 \end{align*}\]

The demand curve is inelastic in this area; that is, its elasticity value is less than one.

Answer from Point \(G\) to point \(H\):

\[\begin{align*} \% \text{ change in quantity} &= \frac{1600-1800}{1700}\times 100\\ &= \frac{-200}{1700}\times 100\\ &= -11.76 \end{align*}\]

\[\begin{align*} \% \text{ change in price} &= \frac{130-120}{125}\times 100\\ &= \frac{10}{125}\times 100\\ &= 8.00 \end{align*}\]

\[\begin{align*} \text{Elasticity of Demand} &= \frac{-11.76\%}{8.00\%}\\ &= -1.47 \end{align*}\]

The demand curve is elastic in this interval.

#### S2

From point \(J\) to point \(K\), price rises from \(\$8\) to \(\$9\), and quantity rises from \(50\) to \(70\). So:

\[\begin{align*} \% \text{ change in quantity} &= \frac{70-50}{(70+50)\div 2}\times 100\\ &= \frac{20}{60}\times 100\\ &= 33.33 \end{align*}\]

\[\begin{align*} \% \text{ change in price} &= \frac{\$9-\$8}{(\$9+\$8)\div 2}\times 100\\ &= \frac{1}{8.5}\times 100\\ &= 11.76 \end{align*}\]

\[\begin{align*} \text{Elasticity of Supply} &= \frac{33.33\%}{11.76\%}\\ &= 2.83 \end{align*}\]

The supply curve is elastic in this area; that is, its elasticity value is greater than one.

From point \(L\) to point \(M\), the price rises from \(\$10\) to \(\$11\), while the \(Q_s\) rises from \(80\) to \(88\):

\[\begin{align*} \% \text{ change in quantity} &= \frac{88-80}{(88+80)\div 2}\times 100\\ &= \frac{8}{84}\times 100\\ &= 9.52 \end{align*}\]

\[\begin{align*} \% \text{ change in price} &= \frac{\$11-\$10}{(\$11+\$10)\div 2}\times 100\\ &= \frac{1}{10.5}\times 100\\ &= 9.52 \end{align*}\]

\[\begin{align*} \text{Elasticity of Demand} &= \frac{9.52\%}{9.52\%}\\ &= 1.0 \end{align*}\]

The supply curve has unitary elasticity in this area.

From point \(N\) to point \(P\), the price rises from \(\$12\) to \(\$13\), and \(Q_s\) rises from \(95\) to \(100\):

\[\begin{align*} \% \text{ change in quantity} &= \frac{100-95}{(100+95)\div 2}\times 100\\ &= \frac{5}{97.5}\times 100\\ &= 5.13 \end{align*}\]

\[\begin{align*} \% \text{ change in price} &= \frac{\$13-\$12}{(\$13+\$12)\div 2}\times 100\\ &= \frac{1}{12.5}\times 100\\ &= 8.0 \end{align*}\]

\[\begin{align*} \text{Elasticity of Supply} &= \frac{5.13\%}{8.0\%}\\ &= 0.64 \end{align*}\]

The supply curve is inelastic in this region of the supply curve.