My calculation gets a value different from slide 6. What is wrong with my calculation? Why I didn't get the IRR of 12.34% for Year 4?

Year 1 Year 2 Year 3 Year 4 Year 5

D. 5 After-tax cash flows-owning $2,141 $2,304 $2,469 $2,635 $2,807

F.7 After-tax cash flows-for sales. $23,509 $27,666 $31,966 $36,430 $41,061

G. ATIRR on equity (D.5+F.7) -14.50% 3.57% 9.63% 12.34% 13.71%