After mistakenly letting the cat out of the bag yesterday, Microsoft has officially unveiled its latest Lumia phones at Mobile World Congress -- and they're pretty tempting if you're looking for a good deal. The new Lumia 640 and 640 XL (can you guess the difference?) are the company's latest budget phones, effectively replacing last year's Lumia 630 and 635. They both include a quad-core Snapdragon processor running at 1.2 gigahertz, a gigabyte of RAM, and 720p display resolutions, but they differ in screen size and camera prowess. The Lumia 640 has a 5-inch screen and an 8 megapixel shooter, while the XL -- Microsoft's first budget phablet -- packs in a 5.7-inch screen and a 13MP Zeiss-lens camera. That's a significant bump from the weak 5MP option in last year's phones, but without a big price increase: The 640, expected in May, will start unlocked at around $155 for its 3G version and $177 for the LTE model. And if you want to get your hands on the XL soon, you're in luck. It's coming later this month for around $211 (3G) and $244 (LTE). As usual, final pricing is up to the retailers.