During a glacier survey, a detector records an echo 60 ms after transmitting a pulse from the surface. The upper 30 m of the glacier is compacted snow, in which the pulse travels at 1500 m/s. Beneath the snow, the pulse travels through ice at 3800 m/s before reflecting at the bottom of the glacier. The recorded time includes the outward and return journeys through both materials.
What is the thickness of the ice beneath the compacted snow?
38 m38\ \mathrm{m}38 m
114 m114\ \mathrm{m}114 m
19 m19\ \mathrm{m}19 m
76 m76\ \mathrm{m}76 m