a quick rule about weight for women: if you're 5', a healthy weight is around 100 pounds, give or take a few. for each inch over 5', add 5 pounds. so at 5'11", you wanna be at or around 155. now depending on your body composistion and bone structure, that number might be higher or lower, but it's generally a good rule to go by.
That depends on how much muscle you have, and where your body fat is located. I think 112 is too low for most women, that are your height. It really just depends on your body type. Whatever you do, be healthy about it.