Last Minute GMATprep PS question

[remarti]

Pearson doesn't provide explanations, so I have no clue how to set this up.
Any help would be appreciated.

Question: In May, X sold 15 used cars. For these 15 cars, the range of the selling prices was $15,000 and the lowest selling price was $4,500. In June, X sold 10 used cars. For these 10 cars, the range of the selling price was $16,500 and the lowest selling price was $6,100. What was the range of the selling prices of the 25 used cars sold by X in May and June?

Answer? $18,100

[llewellyn27]

range in May = 15000
Lowest in May = 4500
therefore highest in may = 19500

Range in June = 16500
Lowest in June = 6100
Higest in june = 22600

Therefore range for all cars sold = 22600-4500 = 18,100

[Motherjane]

Pearson doesn't provide explanations, so I have no clue how to set this up.
Any help would be appreciated.

Question: In May, X sold 15 used cars. For these 15 cars, the range of the selling prices was $15,000 and the lowest selling price was $4,500. In June, X sold 10 used cars. For these 10 cars, the range of the selling price was $16,500 and the lowest selling price was $6,100. What was the range of the selling prices of the 25 used cars sold by X in May and June?

Answer? $18,100

May figure,
Range = $15,000
Lowest Selling price = $4,500
So highest selling price = $(4500 + 15000) = $19,500

June figure,
Range = $16,500
Lowest Selling price = $6,100
So highest selling price = $(6100 + 16500) = $22,600

Range of the SP in both May and June = Highest SP - Lowest SP
= $22,600 - $4,500 = $ 18,100

[remarti]

Thank you llewellyn27 and Motherjane.
After seeing the set up, I can see how the answer was derived.

Pretty simple in hindsight.