While watching a distant lightning storm, a student hears the thunder 4.0 s after seeing the flash. She estimates the distance by multiplying the time delay by the speed of sound at 10 °C (337 m/s). The actual air temperature is 30 °C, for which the speed of sound is 349 m/s. By what percentage did the student underestimate the true distance to the lightning?
a) 3.6 %
b) 1.8 %
c) 3.4 %
d) 4.8 %