Answer:
The answer is: Portland's income will go D: Go up or down half as much as Hadley’s.
Explanation:
We can simulate different total sales movements:
Portland's sales
Current sales 20% increase 20% decrease
$1,000,000 $1,200,000 $800,000
($700,000) ($840,000) ($560,000)
($100,000) ($100,000) ($100,000)
$200,000 $260,000 (+30%) $140,000 (-30%)
Hadley's sales
Current sales 20% increase 20% decrease
$1,000,000 $1,200,000 $800,000
($400,000) ($480,000) ($320,000)
($400,000) ($400,000) ($400,000)
$200,000 $320,000 (+60%) $80,000 (-60%)