A firm orders 12, 30 and 25 items of goods G1, G2 and G3. The cost of each item of G1, G2 and G3 is $8, $30 and $15, respectively.
(a) Write down suitable price and quantity vectors, and use matrix multiplication to work out the total cost of the order.
(b) Write down the new price vector when the cost of G1 rises by 20%, the cost of G2 falls by 10% and the cost of G3 is unaltered. Use matrix multiplication to work out the new cost of the order and hence find the overall percentage change in total cost.