A single$-$family dwelling has a first$-$floor area based on inside dimensions of $142m^2$ and a basement area based on inside dimensions of $137m^2.$ What is the total area in $m^2$ that must be used for the basic load?

a$.,244\mathrm{.}75m^2$

b$.,323\mathrm{.}25m^2$

C$.279m^2$

d$.313\mathrm{.}25m^2$