computer preference

I'm stuck between the army reserve, navy reserve and airforce reserve. I want to be a cyber officer in one of these after graduating with my bachelor's in computer science/engineering. I want to do reserve first then active duty if I like the environment. Which would guarantee me the position...

Yesterday the "Computer Preference (Optional Package)" became available on the Candidate Portal, and I'm wondering if it's worth the $400? I'm thinking that it probably is, and I'll do anything I'm able to make DS' time there easier & more productive. However, I feel the need to due my due...