The Pet War by Allan Woodrow (author) (US edition)

It’s a conflict as old as time itself: dog vs cat, brother vs sister. When Otto asks his family to get a dog, his sister Lexi is just as loud in her desire to get a cat. Their mother wants neither. But she agrees when Lexi comes up with an idea for a competition. Whoever can raise the most money first can decide on which pet the family will get. Soon the stakes rise as the competition grows more fierce by the minute. The Pet War has begun…