What am I doing wrong with part c?

Burrito King (a new fast-food franchise opening up nationwide) has successfully automated burrito production for its drive-up fast-food establishments. The Burro-Master 9000 requires a constant 30 seconds to produce a batch of burritos. It has been estimated that customers will arrive at the drive-up window according to a Poisson distribution at an average of one every 55 seconds. To help determine the amount of space needed for the line at the drive-up window, Burrito King would like to know the following: a. What is the average waiting line length (in cars)? Note: Do not round intermediate calculations. Round your answer to 2 decimal places. b. What is the average number of cars in the system (both in line and at the window)? Note: Do not round intermediate calculations. Round your answer to 2 decimal places. Answer is complete and correct. c. What is the expected average time in the system, in minutes? Note: Do not round intermediate calculations. Round your answer to 2 decimal places. Answer is complete but not entirely correct