Please explain number 4, 5, 7, 8, 9, and 18. Thank you

4. Two point masses a mass a=6 Kg mass and mass 1): 7 kg mass are located L: 5 meters apart. Calculate the moment of inertia about Axis 17. (image not to scale) Axlis a Axis I: 5. Two point masses a 6 Kg mass and an 18 kg mass are connected by a mass less rod 6 meters long. Calculate the distance of the center of mass from the 18 kg mass. Calculate the moment of inertial about an axis located at the center of mass that is perpendicular to the rod. (image not to scale) 7. Two masses a mass a=6 Kg mass and mass b: 9 kg mass are located I; 5 meters apart, each of the masses is a solid sphere of radius 2 meters. Calculate the moment of inertia about Axis b. For a solid sphere I=2l5 NR2 (image not to scale) nds 0 Axis b L -___-.-_ 18. An ice skater has a moment of inertia of 12 kg-m2 when her arms are outstretched. At this time she is spinning at 2.0 radians/s. If she pulls in her arms and decreases her moment of inertia to 6.0 kg-mzand spins at 4.0 radians/s, how much work does she do to pull her arms in? 9. Determine the moment of inertia of a rod about the left end assuming its linear mass density A (its mass per unit length) varies linearly from A = )4) at the left end to double that value, A = 21.0, at the right end. 8. Determine the CM of a rod assuming its linear mass density .1 (its mass per unit length) varies linearly from A = 20 at the left end to double that value, A = 224), at the right end