/sci/ - Science & Math

I need some help with part E. I don't know what I'm doing wrong.

I do the integral and end up with
[math] \frac{\alpha}{4}x^4 + \beta x [/math] evaluated from 0 to [math]7.5*10^4 [/math]

I plug in the numbers and then I solve for [math]KE_2 [/math], but it just doesn't work. I've done it several times and get the same answer repeatedly. What am I doing wrong?