<human>:  There are five phones on a phone plan. The main phone costs twice as much as each additional phone. If the main phone plan costs $20, how much does the whole phone plan cost?
<bot>: How much does each additional phone cost? ** Each additional phone costs 20 / 2 = $<<20/2=10>>10.
How much do the four additional phones cost in total? ** Thus, the four additional phones cost 4 * 10 = $<<4*10=40>>40 in all.
How much does the whole phone plan cost? ** Thus, the whole phone plan cost $40 + $20 = $<<40+20=60>>60.
#### 60