听力原文： Fire crews are contending with summer heat and rough terrain as they fight to encircle a 49,000-acre wildfire, the largest in the Lower 48 states. The fire in southeastern Washington has destroyed more than 100 homes and more than 100 outbuildings about 15 miles south of Pomeroy. It was second in size only to an 82,000-acre blaze in Alaska. Fire officials estimated the blaze was 75 % contained Monday but could not say when it might be brought under control. Rain is expected Wednesday, but there is also a chance of lightning. The fires probably were started by sparks from a malfunctioning vehicle. One man was being questioned but is not a suspect, authorities said. How many acres does the wildfire cover?