A special type of timber can be bought in 3 lengths. The lengths that can be bought and the price of each plank are shown in the table below. Length of plank in metres 2.5 3.5 4.5
Price $2.50 $3.50 $4.50

Sophie needs to buy enough of this type of timber so that by sawing the planks she will have 10 pieces of length 1.50m, 10 pieces of length 2.00m and 10 pieces of length 3.00m.

(a) What is the least that Sophie can pay for the timber that she needs? [2]

Sophie’s project was successful and she decided to repeat it. Unfortunately, when she went back to the timber merchant the prices had changed. The new prices are in the following table.

Length of plank in metres 2.5 3.5 4.5
Price: $2.50 $4.50 $6.00

(b) What is the least she could now pay to get enough timber for her needs? [3]