4. For each of the questions below, provide a justification for your response. a. What does the presence of a row whose entries are all zero in an augmented matrix tell us about the solution space of the linear sys- tem? b. How can you determine if a linear system has no solutions directly from its reduced row echelon matrix? c. How can you determine if a linear system has infinitely many so- lutions directly from its reduced row echelon matrix? d. What can you say the solution space of a linear system if there are more unknowns than equations and at least one solution exists?