The following data, which represent the working hours of a group of workers in a particular factory for a period of three months, find the probability of working hours less than 899.5 * - 400 499 12 -500 599 48 -600 699 56 -700 799 78 -800 899 66 -900 999 66 -1000 1099 46 -1100 1199 20 -1200 1299 8