A building contractor undertakes a job to construct 4 flats on a plot along with parking area. Due to strike the probability of many construction workers not being present for the job is 0.65. The probability that many are not present and still the work gets completed on times is 0.35. The probability that work will be completed on time when all workers are present is 0.80. Let : E_{1} represent the event when many workers were not present for the job; E_{2} represent the event when all workers were present; and E: represent completing the construction work on time. Based on the above information. answer the following questions: (1) What is the probability that all the workers are present for the job?