In the professional videotape recording system known as quadriplex, four tape heads are mounted on the circumference

Question:

In the professional videotape recording system known as quadriplex, four tape heads are mounted on the circumference of a drum of radius 2.5 cm that spins at 1500 rad/s.
(a) At what speed are the tape heads moving?
(b) Why are moving tape heads used instead of stationary ones, as in audiotape recorders?