Solution:
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- Cost of the show is $0.04 * number of attendees, then add $180.

- Revenue is the ticket price multiplied by number of attendees.

- Profit is revenue minus cost.


Price       Attendees   Cost        Revenue     Profit
=======================================================
$5.00       120         184.80      600.00      415.20
$4.00       270         190.80      1080.00     889.20
$3.00       420         196.80      1260.00     1063.20


The best price to seel the ticket is $3.00.