Calculate the market demand function.

The individual demand function is $Q_d = 52 - 2P$, and there are 75 buyers.

The individual supply function is $Q_s = 15 + 10P$, and there are 10 sellers.

The market demand function is $\boxed{Q_{MD} = 3900 - 150P}$ and the market supply function is $\boxed{Q_{MS} = 150 + 100P}$.

• For $P = 5$: $Q_{MD} = 3900 - 150(5) = 3900 - 750 = 3150$ units $Q_{MS} = 150 + 100(5) = 150 + 500 = 650$ units
• For $P = 10$: $Q_{MD} = 3900 - 150(10) = 3900 - 1500 = 2400$ units $Q_{MS} = 150 + 100(10) = 150 + 1000 = 1150$ units
• For $P = 15$: $Q_{MD} = 3900 - 150(15) = 3900 - 2250 = 1650$ units $Q_{MS} = 150 + 100(15) = 150 + 1500 = 1650$ units
• For $P = 20$: $Q_{MD} = 3900 - 150(20) = 3900 - 3000 = 900$ units $Q_{MS} = 150 + 100(20) = 150 + 2000 = 2150$ units

The equilibrium price is $\boxed{\text{15 FCFA}}$.

Using $Q_{MD}$:

The equilibrium quantity is $\boxed{\text{1650 units}}$.

At $P = 20$ FCFA:
$Q_{MD} = 3900 - 150(20) = 3900 - 3000 = 900$ units
$Q_{MS} = 150 + 100(20) = 150 + 2000 = 2150$ units

Surplus = $Q_{MS} - Q_{MD} = 2150 - 900 = 1250$ units.

Cost = Surplus quantity $\times$ Minimum price
Cost = $1250 \text{ units} \times 20 \text{ FCFA/unit} = 25000 \text{ FCFA}$
The cost to