What is (a) the highest, and (b) lowest rate of return (in percent) possible?

help please answer in text form with proper workings and explanation for each and every part and steps with concept and introduction no AI no copy paste remember answer must be in proper format with all working

Waller County is planning to construct a Dam some tens of miles away from the Hempstead Recreation center to facilitate fishing in the El Manny River Basin and Power Generation. The first cost for the Dam will amount to $6,500,000. Annual maintenance and repairs will amount to $24,000 for the first four years, to $28,000 for each year in the next eight years, and to $32,000 per year for the next four years. At the end of the 16th year, $25,000 is estimated to be deposited into Waller county account as tax credits earned for its environmental compliance in the construction and operation of the Dam. In addition a major overhaul costing $650,000 will be required at the end of the seventh year. Use an interest rate of 10% and : a) Determine the engineering economy symbols and their value for each option. b) Construct the cash flow diagram c) Calculate the Capital Recovery for the project

Hollygan Co. must choose between gas-powered and an electric-powered forklift truck for moving materials in its factory. Because both forklifts perform the same function, the firm will choose only one.  (They are mutually exclusive investments.)  The electric-powered truck will cost more, but it will be less expensive to operate; it will cost $110,000, whereas the gas powered truck will cost $40,000.  The required rate of return that applies to both investments is 14 percent.  The life for both types of truck is estimated be 12 years, during which time the net cash flows for the electric-powered truck will be $23,500 per year and those for gas-powered truck will be $10,000 per year.  Calculate the NPV and IRR for each type of truck, and decide which to recommend. (Written work shown please)

Please provide more working out for part (b). Greatly Appreciated!!