4-60. Maintenance expenses

 4-60. Maintenance expenses for a bridge on the OhioRiver are estimated to be $20,000 per year for thefirst 8 years, followed by two separate $100,000expenditures in years 12 and 18. The expected life ofthe bridge is 30 years. If i = 6% per year, what isthe equivalent uniform annual expense over the entire30-year period?