15 The diagram shows the lines x + y = 8 and 2y = x + 4. (a) The shaded region on the diagram is defined by three inequalities. Write down these three inequalities. (b) Another region, R, is defined by the inequalities x + y =< 8 , 2y =< x + 4 and y => a, where a is an integer. This region contains 5 points with integer coordinates. Write down the value of a.