A Spaceship Approaches Earth with a Speed $0.50$ C a Passenger in the Spaceship Measures His Heartbeat as Passenger

Multiple Choice

A spaceship approaches Earth with a speed $0.50$ c. A passenger in the spaceship measures his heartbeat as 70 beats per minute. What is his heartbeat rate according to an observer that is at rest relative to Earth?

A) 75 beats per minute
B) 69 beats per minute
C) 65 beats per minute
D) 73 beats per minute
E) 61 beats per minute