The formula C=3.14d can be used to approximate the circumference of a circle given its diameter. Company A manufactures and sells a certain washer with an outside circumference of 12 centimeters. The company has decided that a washer whose actual circumference is in the interval 11.9 ≤ C ≤ 12.1 centimeters is acceptable. Use a compound inequality and find the corresponding interval for diameters of these washers.