The flow in a river can be modeled as a log-normal distribution. From the data, it was estimated that, the probability that the flow exceeds 969 cfs is 50% and the probability that it exceeds 100 cfs is 90%. Let X denote the flow in cfs in the river. Flood conditions occur when flow is 5000 cfs or above. To compute the percentage of time flood conditions occur for this river, we have to find, P(X≥5000)=1-P(Z