a$)(10\%)$ Create a submatrix named D from A$,$ without the first row and first column.

b$)(10\%)$ Combine vector B and vector C to create a single matrix named E with $2$ rows and $6$ columns. Replace any missing values with zero.

c$)(10\%)$ Create a matrix H with $4$ rows and $50$ columns and with values starting from $0$ to $.$

d$)(5\%)$ Save all the matrices created to a file, clear the workspace and load only matrix H from the file.