A high-end interior designer charges an hourly rate for his services plus a consultation fee. As a courtesy to his clients, after working on a job for over 20 hours, his hourly rate drops and the consultation fee is waived. The fees for the interior designer's services can be modeled with the following piecewise equation, where x represents the number of hours. f(x)= { 150x + 300, x ≤ 20
{ 100x, x > 20

How much would it cost for 18 hours of interior design services?

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