$$ \begin{cases} 1\ut{acre}=&40\ut{perch}\times4\ut{perch}=&160\ut{perch^2}\\ 1\ut{rood}=&40\ut{perch}\times1\ut{perch}=&40\ut{perch^2}\\ 1\ut{perch}=&16.5\ut{ft} \end{cases} $$ $$\ab{a}$$ $$ \begin{aligned} \Ans=&2.80\ut{acre}+13.0\ut{perch}\times3.00\ut{perch}\\ =&2.80\ut{acre}\cdot\frac{160\ut{perch^2}}{1\ut{acre}}+39\ut{perch^2}\\ =&487\ut{perch^2}\\ =&487\ut{perch^2}\cdot\frac{1\ut{rood}}{4..