Suppose that the ﬁrm has two possible activities to produce output. Activity $A$ uses $a_1$ units of good $1$ and $a_2$ units of good $2$ to produce $1$ unit of output. Activity $B$ uses $b_1$ units of good $1$ and $b_2$ units of good $2$ to produce $1$ unit of output. Factors can only be used in these ﬁxed proportions. If the factor prices are $(w_1,w_2)$, what are the demands for the two factors?
Please help me with this question as I don't know what to do when there are two simultaneous activities involved.thank you