Please answer correctly

Determine whether the following statements are true and give an explanation or counterexample. bold a. when using the shell method, the axis of the cylindrical shells is parallel to the axis of revolution. bold b. if a region is revolved about the y-axis, then the shell method must be used. bold c. if a region is revolved about the x-axis, then in principle it is possible to use the disk/washer method and integrate with respect to x or the shell method and integrate with respect to y.

What is the area of the triangle 10 13 12

Out of 50 students surveyed, 16 have a dog. based on these results, predict how many of the 280 students in the school have a dog.