NPV and IRR Calculations when Cash Flows Change

All

Am new here and apologize in advance if this question has been asked.

The case involves how to compare and calculate NPV/IRR when project cash flows change, and how best to compare the new NPV/IRR values with the original NPV/IRR, as follows:

A B
year original cash flows cash flows new in yr 4 Comments
0 -100 -100 investment at end of yr 0
1 -10 -10
2 -10 -10
3 -10 -10 costs change and sales price change so new cash flows
4 -10 -50
5 -10 -50
6 150 200
7 150 200
Total 150 170
NPV10 $21.6 ???
IRR 13% ???

Scenario
Original NPV calculated for cash flows in column A.
While project is in progress in year 3, costs and prices change so cash flows have been revised as shown in column B

Questions:

How to calculate NPV and IRR so comparison between Columns A and B - how have NPV/IRR changed?
Should Column A & B cash flows be discounted starting at Yr 3, or at Yr 0?
If discounted starting at Yr 3, what would the excel formula be to compare Column A and B cash flows?

Apologies for the table formatting above - not sure how to insert an excel item - it looks fine when I edit it but when posted formatting is gone.

Thanks in advance for any comments.

If I enter =NPV(0.1,A cash flows), I get 21.58. =IRR(A cash flows) gives 13.09% -- in line with what you show in your OP. I don't understand what you are wanting to do. Wouldn't you just enter NPV(0.1,B cash flows) and IRR(B cash flows) to get the NPV and IRR for that scenario (23.15 and 12.96%)? Then make any comparison that you would want to do (Scenario B seems to have a larger NPV and a slightly smaller rate of return)?

I am familiar with the basic syntax of these functions, and I can easily lookup the syntax of functions I don't know in the help files, but I do not know much about finance and business math. It sounds like you understand the syntax of the NPV() function, but are not sure of the business math side of the question about how to correctly compute the NPV for the second scenario. I'm afraid I cannot help with that. I know we have a few users here who are savvy about financial calculations, who may be able to advise you on the correct approach for this NPV problem. Once someone comes on an explains the applicable business math principles, they (or any of us) can probably help with the Excel function syntax.