please code in c

$3\mathrm{.}6$ Implement matrix$-$vector multiplication using a block$-$submatrix distribution of

the matrix. Assume that the vectors are distributed among the diagonal pro$-$

cesses. Once again, you can have process $0$ read in the matrix and aggregate the

submatrices before sending them to the processes. Assume comm$\_$sz is a perfect

square and that $\sqrt[\phantom{2}]{\text{c}\text{o}\text{m}\text{m}sz}$ evenly divides the order of the matrix.