I already have the answer to step A$.$ Need help with step B$.$

A certain service can be performed by one of two machines. Machine R has a first cost of

$$8,000,$ and is expected to lead to annual profits of $$2,000$ per year during its $10-$year life.

Machine Q has a first cost of $$18,000$ and an annual profit of $$4,000$ per year, but will last for

$20$ years.

a$)$ Determine the present worth of each project, using the least common multiple $($LCM$)$ of

lives, and a discount rate of $8\%.$ Solution: $()=$ $$7931$ and $()=$ $$21272$

b$)$ Does the decision from part a$)$ depend on the discount rate? What is the approximate discount

rate at which the decision would change? Hint: To find this out, you can use Excel to create a graph

similar to the one we discussed in Lecture $5($see here$).$ Please attach a screenshot of the graph you

generate. Solution: Yes, the decision does depend on the discount rate, and it changes at around a

$22\%$ discount rate