A maintenance engineer is inspecting pipework in a controlled area of a nuclear power station. The planned maximum dose for the task is 25 μSv25\ \mu\mathrm{Sv}25 μSv.
The engineer's personal dosimeter shows that a dose of 10 μSv10\ \mu\mathrm{Sv}10 μSv has already been received during the task. In the next area of pipework, the dose rate is constant at 30 μSv30\ \mu\mathrm{Sv}30 μSv per hour.
What is the greatest additional time the engineer can spend in this area without exceeding the planned maximum dose?
30 minutes30\ \mathrm{minutes}30 minutes
20 minutes20\ \mathrm{minutes}20 minutes
15 minutes15\ \mathrm{minutes}15 minutes
50 minutes50\ \mathrm{minutes}50 minutes