6. A firm is presently using a machine that has a market value of $11,000 to do a specializec production job. The requirement for this operation is expected to last only 6 years more, after which it will no longer be done. The predicted costs and salvage values for the present machine are: 1 234 5 6 Year Operating cost $1,500 $1,800 $2,100 $2,400 $2,700 3,000 Salvage value $8,000 $6,000 $5,000 $5,000 $3,000 $2,000 A new machine has been developed that can be purchased for $17,000 and has the following predicted cost performance. Year 2 4 5 Operating cost $1,000$1,100 $1,200 $1,300 $1,400 $1,500 Salvage value $13,000 $11,000$10,000 $9,000 $8,000 $7,000 a. If interest rate is at 0%, when should the new machine be purchased (if it should be purchased)? b. If interest rate is at 15%, when should the new machine be purchased (if it should be purchased)