SAVE $400: The Mammotion LUBA 3 AWD 5000H robot lawn mower is on sale at Amazon for $2,899, down from the list price at Mammotion of $3,299. That's a 22% discount and the lowest we've seen at Amazon. $2,899 at Amazon $3,299 Save $400 By now, the lawn is rejoicing. It made it through the winter chill and it's flourishing with mild spring temperatures, occasional rain, and plenty of sun. That's all great until it comes time to mow the grass. If you're not in the mood to deal with another household chore, consider offloading the task to a robot lawn mower. There's a powerful model on sale at Amazon today. As of May 12, the Mammotion LUBA 3 AWD 5000H robot lawn mower is on sale at Amazon for $2,899, down from the list price at Mammotion of $3,299. That's a 22% discount that takes $400 off the normal price. It's also the lowest we've seen at Amazon.…