1. A vibrating point on a spring travels 60 mm during three cycles. What is the amplitude of the vibration?

a) 0.05 mm
b) 5.0 mm
c) 15.mm
d) 20.mm
e) 180 mm
my answer: I got 10 mm but it is not listed as an option

2. When a tuning fork of unknown frequency is sounded simultaneously with a 512 Hz tuning fork, 20 beats are heard in 4.0 seconds. What are the possible frequencies of the unknown tuning fork?