Operating systems might contain which of the following components? Select one: a. All of these are true O b. A graphical user interface C. A command-line interface O d. A firewall and other security measures

For positive constants a and b, the force between two atoms in a molecule is given f(r) = −a r2 + b r3 , where r > 0 is the distance between the atoms. note: a and b are upper case letters. (a) find f '(r) = (b) find the critical point for f(r). r = (c) find f ''(r) = (d) find the value of r so that f ''(r) = 0.