Hello!!:) can you please guide me through the formulas to answer these questions? (best if not done in Excel, but okay if it is - as long as it's in simpler terms for me to understand). Thank you xx

Consider two farms operating under a 10 -year time horizon (t=1 to t=10). The Reactive Farm has lower weed control costs than the Proactive Farm initially. However, for the proactive farm, weeds become resistant to glyphosate starting in year 5(t=5). Once resistance develops, maize yields on the Reactive Farm fall 20% (to 5.6 ) and weed control costs rise by R250. Assume all price and cost numbers are constant (in real terms) throughout the 10 -year planning horizon. Assume as discount rate of 5%. 1. What is the net present value of farming over the 10-year planning horizon for the Proactive Farm? 2. What is the net present value of farming over the 10 -year planning horizon for the Reactive Farm? 3. Now, instead of thinking of the problem as for two separate farms, think of it as one farm deciding between two strategies: a proactive strategy and a reactive strategy. What is the gain in NPV over 10 years of following the proactive strategy compared to the reactive strategy (hint: compare your answers to 1 and 2) ? How many years does it take for the proactive strategy to pay for itself? In other words, is the NPV higher under the proactive strategy after 3 years? After 5 years? What's the first year n where the n-year NPV is higher under the proactive strategy