Official Solution: In a certain regional sales company, Marcus earns a monthly salary of $1500, plus 10% of the amount by which his total sales exceed $3000. How much did Marcus earn in April? Marcus’s earnings in April can be expressed as \(1500 + 0.1 * (S - 3000)\), where \(S\) is his total sales.
(1) The amount Marcus earned in April was equal to 25% of his total sales that month.
This gives: \(1500 + 0.1 * (S - 3000) = 0.25 * S\). We can solve for \(S\) and calculate earnings. Sufficient.
(2) If Marcus had made $4000 more in sales in April, his earnings would have been equal to 20% of that higher sales amount.
This implies: \(1500 + 0.1 * (S + 4000 - 3000) = 0.2 * (S + 4000)\). We can solve for \(S\) and calculate earnings. Sufficient.
Answer: D