A child wanders slowly down a circular staircase from the top of a tower. With x, y,zx, y,z in feet and the origin at the base of the tower, her position tt minutes from the start is given by x = 10cos t, y = 10sin t, z = 90 - 5t.

(a) How tall is the tower?

(b) when does the child reach the bottom?

(c) What is her speed at tme t?

(d) What is her acceleration at time t?

Anew test for ra is being developed. the test is administered to 750 patients with ra and 750 without ra. for the sake of the question, assume the prevalence of ra in this population is 50%. of the 750 patients with ra, 575 have a positive result. of the 750 patients without ra, 150 have a positive result. what is the positive predictive value of the new test? a575/(575+150) b. 600/(600+ 150) c. 575/(575+125) d. 600/(600+ 125)