1 answer
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If the observer is x ft from the spot below the balloon,
h = height at 10:00
s = height at 10:10
h/x = tan30°
s/x = tan34°
so
h/tan30 = s/tan34
s = h tan34°/tan30° = 1.168h
at 10:30 the height will be 1.505h
1.505tan30° = tan40.98°
so I guess C is the best choice.