3. A factory packed its products into 3 kinds of boxes, namely small, medium

and large. The weights of each small. medium and large box were 18kg,

25 kg, and 40 kg, respectively. There were altogether a small, b medium and

c large boxes.

a. Write down the formula for the total weight W (in kg) of the 3 boxes.

b. Find the total weight if a = 10, b = 8 and c = 5.​