Answer :
we have to divide 15 over 150
[tex]\frac{15}{150}=\frac{1}{10}=0.1[/tex]so the unit cost is $0.1
and now, we have to divide 6 over 0.1 to get the amount of copies that will cost $6
[tex]\frac{6}{0.1}=60[/tex]so we have that 60 copies will cost $6