Marketopia's real GDP was $520 billion in 2014 and $550 billion in 2015. Its population was 150 million in 2014 and 155 million in 2015. On the other hand, Econland's real GDP was $200 billion in 2014 and $210 billion in 2015, and its population was 53 million in 2014 and 55 million in 2015. Which of the following statements is true?
a. Marketopia's real GDP growth in 2015 is higher than Econland's.
b. Econland's real GDP growth in 2015 is higher than Marketopia's.
c. Marketopia's real GDP growth in 2015 is identical to Econland's.
d. Marketopia's and Econland's real GDP growth rates in 2015 are both higher than 10%.