(a)  State four characteristics of igneous rocks.                                             .                       

(b)  The table below illustrates the combined demand and supply schedule for maize. 
       

Use it to answer the questions that follow.

(i)  Draw the demand and supply curves to show the equilibrium price of maize.              
 

(ii)  Determine the excess demand for maize at a unit price of ₦4.                                            

(iii)  Determine the excess supply for maize at a unit price of ₦12.