題組內容

There are 8 problems in this test. Note that you should write down detailed steps for the solution to each problem； otherwise, no credits for that problem will be given. 
1. Determine the number of integer solutions of x1 + x2 + x3 + x4 = 64, where

(a) 61dfb6acf3eac.jpg ≥ 1,1 ≤ i ≤ 4.