Answer
10
Work Step by Step
Alternative 1: Select battery-powered radar detector:
....... STEP 1: select model type ... 2 choices
....... STEP 2: select detection type ... 3 choices
(Total alternative 1 = 2(3)=6)
Alternative 2: Select cigarette lighter socket-powered:
....... STEP 1: select model type ... 2 choices
....... STEP 2: select detection type ... 2 choices
(Total alternative 1 = 2(2)=4)
TOTAL=... addition principle, 2 alternatives...=4+4=10
