Which of these is an example of a random sample? a. a random fan asks for the band to play her favorite song at the next concert. b. walter asks his three friends whether or not they enjoyed the concert. c. the band manager picks a person in the first row to go backstage at a concert. d. five people are chosen randomly from a crowd of people at a concert.

Find a parametrization for the curve「and determine the work done on a particle moving along γ in r3 through the force field f: r^3--r^3'where f(x,y,z) = (1,-x,z) and (a) im (γ) is the line segment from (0,0,0) to (1,2,1) (b) im (γ) is the polygonal curve with successive vertices (1,0,0), (0,1,1), and (2,2,2) (c) im (γ) is the unit circle in the plane z = 1 with center (0,0,1) beginning and ending at (1,0,1), and starting towards (0,1,1)