Step by Step please. Only with formula, no excel. thanks!

(10 pts) 2. A water pump to be used by the city's maintenance department costs $10 000 new. A running-in period, costing $1000 immediately, is required for a new pump. Operating and maintenance costs average $500 the first year, increasing by $300 per year thereafter. The salvage value of the pump at any time can be estimated by the decliningbalance rate of 20 percent. Interest is at 10 percent A. How often should the pump be replaced? B. If the water pump is being considered to replace an existing one with a salvage value of $1000 (will retain this salvage value indefinitely), and current annual operating cost of $2500 that will rise by $400 per year, thereafter Should the current pump be replaced? When