Today is $1$ January $2024.$ Ella used $$200,000$ to purchase a florist business in Sydney. To operate this business, Ella needs to pay rent, maintenance costs, and labor costs. Here are the details: $$ Rent will be paid by the end of each month with an amount of $$2,000.$ Labor cost will be paid by the end of each month with an amount of $$10,000.$ Maintenance cost will be paid by the end of each quarter with an amount of $$500.$ Ella predicts that this florist franchise initially can have monthly revenue of $$13,000.$ Assume that Ella can obtain this amount by the end of each month. Ella forecasts that this revenue amount will increase at the rate of y$\%$ p$.$a$.$ The revenue increase will only happen at the beginning of each year. For example, this florist franchise initially has monthly revenue of $$13,000$ in $2024.$ Then the revenue amount will become $$13,000(1+$y$\%)$ per month in $2025$ and $$13,000(1+$ y$\%)2$ per month in $2026.$ Ella plans to run this business for three years and predicts that she can sell this business on $1$ January $2027$ with an amount of $$240,000.$

a$.$ Calculate the monthly net cash flows. Assume that Ella can reinvest all profit at a rate of $4\mathrm{.}5\%$ p$.$a$.$ Use Goal Seek to find revenue increasing rate y$\%$ p$.$a$.$ if Ella requires a holding period yield rate of $7\mathrm{.}5\%$ p$.$a$.$ for this investment $($from $1$ January $2024$ to $1$ January $2027).$