Answer:

Step-by-step explanation:
The sum of the first 10 terms of an arithmetic sequence is:


the sum of the second 10 terms is: a₁₁ + a₁₂+...+ a₂₀
And the sum of the first 20 terms of an arithmetic sequence is:

so the sum of the second 10 terms is:
Therefore we have:

and:

The unit rates is $40 $160 divides by 4 calculators gets you $40