please answer all the questions from a to d. Thank you

6. (a) An optimization model has the single constraint x1+x28, and the only non-negativity restriction is x10. Make a graph and show the edge of the feasible region. (b) Consider a model of the form min c1x1+c2x2, where the coefficients c1 and c2 may be positive or negative. (i) Find any values of c1 and c2 which create a unique optimal solution. (ii) Find all the values of c1 and c2 which create a unique optimal solution. (c) As above for the creation of multiple optima. (d) As above for the creation of an unbounded solution