Генерировсние элементов матрицы ( generate elements of matrices)

Generate elements of a matrices C nxm and D mxn by random drawing
(function srand() should be employed) of numbers from range -10,…,10.
Multiply the matrices CxD and draw a vector B {nx1} from random numbers
within a range -2,…,2. Then solve a system:
CxDx{X}={B},
using Gauss elimination method. Interpolate the results within the
range (1,…,n) in k points.

 Проект надо сделать в С, а не в С++!!. Большая просьба писать самым простым  способом.