Answer: t=72.5secs and f= 0.194Hz
Explanation:
0.938=e^[-bt/(2M)]
ln(0.938) = -(0.113 kg/s)(t) / [2(64.0 kg)]
t = 72.5 s
ω = sqrt[k/m - {b/(2M)}²]
ω = sqrt[(113 N/m)/(64.0 kg) - {(0.113kg/s)/(2(64.0 kg))}²]
ω = 1.33 rad/s
2πf = 1.33 rad/s
f = 0.194 Hz