Question 4 a. The demand for petroleum is given by QD=85 GAP where Q Dis the quantity demanded in thousands of barrels per day and P is the price per barrel in dollars. The supply of petroleum is given by QS=55+0.6P. Calculate the equilibrium price and quantity in this market. [4 marks] b. In the context of the problem in part (a), calculate the demand and supply for petroleum it the market price is $15 per barrel. What problem exists in the economy. [4 marks] c. As more people buy televisions, the demand for Cable services increases and the price of Cable services decreases. The fall in the price of Cable service decreases the supply of Cable service.\" Explain what is wrong with this statement. [3 marks]