Consider the function f left parenthesis x right parenthesis equals x cubed minus 6 x squared plus 9 x. On what interval(s) is f open parentheses x close parentheses both increasing and concave up? A.) open parentheses 2 comma space infinity close parentheses B.) open parentheses short dash infinity comma space 1 close parentheses union open parentheses 3 comma space infinity close parentheses C.) open parentheses 2 comma space 3 close parentheses D.) open parentheses 3 comma space infinity close parentheses