Currently, it takes Mia 5 hours to read 200 pages, which means that she reads 40 pages an hour. If she works at twice this rate, she would be able to read 80 pages an hour. This means that it would take her 100/80 = 1.25 hours to read 100 pages. 1.25 hours is equal to 1.25*60 = 75 minutes, or A.