5. Nine pieces of wood are required to build a small cabinet. The lengths, in cm, of the pieces of wood are listed below. $$20 , \quad 20 , \quad 20 , \quad 35 , \quad 40 , \quad 50 , \quad 60 , \quad 70 , \quad 75$$ Planks, one metre in length, can be purchased at a cost of \(\pounds 3\) each.

1. The first fit decreasing algorithm is used to determine how many of these planks are to be purchased to make this cabinet. Find the total cost and the amount of wood wasted.
   (5) Planks of wood can also be bought in 1.5 m lengths, at a cost of \(\pounds 4\) each. The cabinet can be built using a mixture of 1 m and 1.5 m planks.
2. Find the minimum cost of making this cabinet. Justify your answer.
   (4)