Whats the Maximum a swimmer can drop in a year

Question
Hello my name is David and I have 2 years in USA. I would like to know if I can drop 5 or 6 second in one year practice very hard with 10 practice in the week and swimming around 100 KM in the week I swim now for USA swimming but  I want to apply for a scholarship and the coach told me that I need to have 46 or 47 in the 100 yr free and 1:46 in the 200 and 21 in the 50 and my best time are 52 in free 23 in the 50 and 1:53 in the 200 so i would like to know if i can do it, or what the maximum that a person can drop swimming very hard in a year, I am really disapponted now because Ii have'nt drop for so long and I think that the best thing that I can do is to quit but I want to consult and talk it with people that know better that in the  swimming field. I also want to know how many years I need for be in shape again I stop to swim for 4 years and now I came back one year ago i hope that you can help me; Thank you very much, appreciate it

Answer
David-
Sorry it took so long.  I have seen drops that big from some people, so it is possible, I have done it myself when I was competing.  It sounds like your are training enough, but you need to make sure you're training the right way.  There is a saying "Practice doesn't make perfect, Perfect practice makes perfect!"  This means that the amount of time and distance, though important,doesn't mean much if it is done sloppy and lazy and without thought.  You need to make sure your strokes are technically as good as possible.  And one thing that I always emphasize with my athletes is starts, turns and streamlines off the walls.  Practice good strong streamlines every time you push off the wall, try to get past the backstroke flags every time.  Also work on not taking a breath with your first stroke, take at least one stroke before breathing.
I hope this helps and good luck I hope you drop the time and get the scholarship.
As a back up, if you can't make it to a Div. I school, Div.II schools are a great choice and some do offer scholarships.
Again, Good Luck.