A monkey climbs 30 feet at the beginning of each hour and rests for a while, then he slips back 20 feet before he again starts climbing in the beginning of the next hour. If he begins his ascent at 8 a.m., at what time will he first touch a flag at 120 feet from the ground?
1
4 p.m.
2
5 p.m.
3
6 p.m.
4
None of these