Question: From records for two nearby drainage systems, A and B, during storms or downpours, the demand placed on each of the drainage system in litres per minute was considered. It was found that the average demand and standard deviation for A were 74.4 l/min and 2.54 l/min respectively, and for B were 69.4 l/min and 1.95 l/min respectively, and that the correlation between the demands was 0.7. Assuming that the demands placed on drainage systems are normally distributed, what is the probability that the demand on A exceeds the demand on B? (Show your working)