Cross training for Cross Country?

I am trying to figure out my training plan for cross country next season. I’m a frosh boy and my pr is 19:07. I want to get to 17:40′s for most of next season. I was thinking about 50 miles of running and about 100 miles of biking each weak. Will this be a good plan or will biking work the wrong muscles for running. Either this or more running and less biking.
Yeah i am not just gonna do easy slow runs to get the mileage up. in the 50 i am counting speed days and stuff. And where i live i can’t run a mile without hitting a hill. On my normal routes there are mile long hills with 10% grades. (where i do my speedwork)

Cross country training questions…?

Hey, I’m a freshman in high school and finished my first season running XC in November. I took about a month off of running because my doctor told me I was at high risk for stress fractures, and then I started softball training. However, softball training at my school involves very little running, and I really want to start working NOW to get my times down for next fall’s cross country season. I have about 6 months until summer workouts with the team begin, and 8 months until competition.

Is it possible to knock off 3 or 4 minutes off my 5K time? Can anyone tell me how much I should increase my mileage each week if this week I am starting with 2.75 miles a day? Can anyone give me advice on eating, cross training, mile plans? Thanks so much!