A store sells a certain product at a fixed price per unit. At the product's current price, \(q\) units cost a total of exactly \(\$300.\) If the price were lowered by \(\$5\) from its current value, then \(q + 2n\) units would cost exactly \(\$300;\) if the price were raised by \(\$5,\) then \(q - n\) units would cost exactly \(\$300.\) What is the value of \(q?\)
A. 10
B. 15
C. 20
D. 25
E. 30
Answer: C
Source: Manhattan GMAT