I am an Introduction to Upper Level Physics survey course at a university, but I need help with particle physics. I was given the following two problems (see attached images, from University Physics 11e by Young and Freedman). To solve them, I tried to divide the total energy by the number of particle, for example, by this method I got 50 GeV for problem 40.15, part (a). However, using this same method does not match the solutions in the back of the book for part (b). Can anyone please help?