Suppose that the daily output of a production process is $90,000$ units, and the labor and materials costs are $$30,000$ and $$20,000,$ respectively. What is the multi$-$factor productivity of this process?

$9\mathrm{.}00$

$1\mathrm{.}80$

$3\mathrm{.}00$

$4\mathrm{.}50$