Students are going through a three-step process to obtain their ID cards. Each student will spend 3 minutes at the single registration desk before going to one of three cashiers to pay a fee for the card. After that, he/she will visit one of four ID processing stations to have his/her picture taken and the ID card printed. Registration takes 3 minutes. Visits to the cashier and ID processing station take 9 and 18 minutes respectively. If the demand rate is 2/10 students per minute, calculate the flow rate in students per minute (accurate to three decimal places)?