I only need help with question C

A new computer system will require an initial outlay of $22,000, but it will increase the firm's cash flows by $4,400 a year for each of the next 7 years.

a.Calculate the NPV and decide if the system is worth installing if the required rate of return is10%.(Negative amount should be indicated by a minus sign. Do not round intermediate calculations. Round your answers to 2 decimal places.)

-578.95

b.Calculate the NPV and decide if the system is worth installing if the required rate of return is15%.(Negative amount should be indicated by a minus sign. Do not round intermediate calculations. Round your answers to 2 decimal places.)

• 3694.16

c.How high can the discount rate be before you would reject the project?(Do not round intermediate calculations. Enter your answer as a percent rounded to 2 decimal places.)

????