You know that:
- An average of 639 copies per hour can be produced by the main printer.
- The cost for electricity and supplies is $0.06 for every 36 pages produced.
- The library is opened for 12 hours.
Let be "x"the cost (in dollars) for electricity and supplies for 639 copies produced in 1 hour.
You can set up the following proportion:
![(0.06)/(36)=(x)/(639)](https://img.qammunity.org/2023/formulas/mathematics/college/dfv561vrajb5tpirjj8lczyng4t7e2pk9u.png)
Solve for "x":
![\begin{gathered} ((0.06)/(36))(639)=x \\ \\ x=1.065 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/2u3eszaiz8hv6uhtdgru3gb40ei1che2q1.png)
Knowing that the cost for electricity and supplies for 639 copies produced in 1 hour is $1.065, youo can multiply it by 12, in order to calculate how much money the college uses on printing each day:
![(1.065dollars\text{)}(12)=12.78dollars](https://img.qammunity.org/2023/formulas/mathematics/college/4817tumzbqp6kgawjua99ljlosjufhluks.png)
The answer is: The college uses $12.78 on printing each day.