How can I do this on excel. An office building should last $60$ years, but this owner will sell it at $20$ years for $40\%$ of its construction cost. For the first $20$ years it can be leased as Class A space, which is all this owner operates.$$

When the building is sold, the land's cost will be recovered in full.

$$2\mathrm{.}2$M$$Land

$$4\mathrm{.}1$M$$Building

$$640,000$Annual operating and maintenance$$

$4\%$Annual property taxes and insurance $(\%$ of initial investment$)$

a$)$ If the owner wants a $12\%$ rate of return, what is the required monthly leasing cost?

b$)$ Assuming that the building is vacant $5\%$ of the time, what is the required monthly lease?

c$)$ What is an example of monthly cost per square foot for Class A space in your community?