pls help me w this, I've been doing this since 5 minutes ago

Answer:
t=0.0625s
Explanation:
F=number of swings/time taken
DATA
Frequency=4.0Hz
number of swings from Q to R
=1/4
time taken=?
Frequency=number of swings/time taken
make t the subject of the formula
t=n/f
substitute the given date
t=0.25/4.0
t=0.0625s
option A is collect