Please help check if I am doing it correct, thank you!

Major expenses of $5000 all ocar at EOY 2 and continue every 3 years up to year 11 . The interest b=8% a) Drave cash flow b) Iresent equivalent P0 c) Anual equivalent during year 311 a) b) P0=5000(1/F,8%,2)+5000(1/F,8%,5)+5000(1/F,8%,8)+5000(1/F,8%,11) c) P2=5000(1/F,8%,3)+5000(2/F,8%,6)+5000(1/F,8%,9) A31=P2(A/I,8%,9)