Suppose the demand and supply curves of coffee are given by:

qD = 1,000 –- p,

qS = 700 + 2p

Calculate equilibrium quantity.

900

The correct answer is option 3: 900

At equilibrium, market supply = market demand.

Equating them,

we get 1000-p = 700+ 2p

          or 1000-700 = 2p + p

           or 300 = 3p

          or 100 = p

Putting p = 100 in any equation, we get

q = 1000-p = 1000-100 = 900.

So equilibrium quantity is 900.