I'm am confused on what perpetual life is

Memphis Light, Gas and Water Division is exploring the possibility of installing hydrokinetic turbines in the Mississippi River to generate power for the Memphis and Shelby County area. Consulting engineers have identified two potential types of hydrokinetic turbines to meet the needs of MLG8&W. The costs and expected income for the two types of turbines are shown in the table below. Using a perpetual annual worth analysis and a MARR of 6% per year, determine which type of hydro kinetic turbine, if any, should be selected. Complete all calculations to the nearest dollar. Memphis Light, Gas and Water Division is exploring the possibility of installing hydrokinetic turbines in the Mississippi River to generate power for the Memphis and Shelby County area. Consulting engineers have identified two potential types of hydrokinetic turbines to meet the needs of MLG8&W. The costs and expected income for the two types of turbines are shown in the table below. Using a perpetual annual worth analysis and a MARR of 6% per year, determine which type of hydro kinetic turbine, if any, should be selected. Complete all calculations to the nearest dollar