Help determine Q1 and Q3 please

The following data represent the monthly phone use, in minutes, of a customer enrolled in a fraud prevention program for the past 20 months. The phone company decides to use the upper fence 422 447 321 423 as the cutoff point for the number of minutes at which the customer should be contacted. What is the cutoff point? 454 507 337 416 308 390 355 406 307 430 431 513 370 361 315 424 The cutoff point is minutes. (Round to the nearest minute.)