6. (20%) (a) (10%) An engineer wishes to calculate a project's present worth with estimated costs (in actual dollars) of $35,000 now and $7,000 per year for 5 years beginning 1 year from now, with increases of 12% per year thereafter for the next 8 years. Use an inflation-free interest rate of 15% per year and general inflation rate of 11% per year to calculate the equivalent present worth. (b) (10%) Suppose that you borrow $25,000 (constant dollars) at 12% compounded monthly over 5 years. The 12% represents the annual market interest rate. If the average monthly general inflation rate is 0.5%, determine the monthly inflation-free interest rate and equivalent equal monthly payment series in constant dollars