Read the following passage and answer the questions.

Suppose there is a market consisting of identical firms producing the same quality of salt.

Suppose the market demand curve and the market supply curve for salt are given by:

$Q_D=350-p$ for $0 ≤ p ≤ 350$

= 0 for p > 350

$Q_S = 220 + p$ for $p ≥10$

= 0 for 0 ≤ p < 10

Where $Q_D$ and $Q_S$ denote the demand for and supply of salt (in kg) respectively and p denotes the price of salt per kg in rupees.

Which of the following expressions will be used for calculating excess supply of salt in the market?

$2(p - 65)$

The correct answer is Option (3) → $2(p - 65)$ 

$Q_D=350 - p$

$Q_S = 220 + p$

Excess Supply = $Q_S-Q_D$

                       = ​220 + p - (350 - p)

                      =  2p - 130

                      = 2 (p - 65)

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