The following table gives the cumulative frequency distribution of the commuting time (in minutes) from home to work for a sample of 400 persons selected from a city.
|
Time (minutes)
|
f
|
|
0 to less than 10
|
65
|
|
0 to less than 20
|
155
|
|
0 to less than 30
|
227
|
|
0 to less than 40
|
286
|
|
0 to less than 50
|
347
|
|
0 to less than 60
|
400
|
What is the cumulative frequency of the fourth class? (rounded to 4 decimal places)