2010007207
Level:
B
The measures of given angles belong to the set \( M \):
\[ M = \left\{ 150^{\circ} + k\,360^{\circ}\right\},\ k\in\{-1;0;1\}.\]
Determine their arithmetic mean.
\( 150^{\circ} \)
\( 90^{\circ} \)
\( -90^{\circ} \)
\( -150^{\circ} \)