The number of people visiting the zoo during weekends is given below. If the modal class is \(15 - 30\) with mode 28, then find the missing frequency.
 
Age \(0 - 15\) \(15 - 30\) \(30 - 45\) \(45 - 60\) \(60 - 75\)
Number of people 8 47 \(a\) 37 10
 
Answer:
 
The missing frequency is .