Thomas bought a new truck in Calgary with a list price, including options, of $21,000. The dealer had given her a “generous trade-in allowance ?of $5,000 on her old truck that had a wholesale price of $3,000. GST was $800. The annual cash operating costs of the old truck were $4,200. The new truck was expected to reduce these costs by one-third, to $2,800 per year. Compute the amount of the original investment in the new truck. Explain your reasoning.