The life of a tube (X1) and the filament diameter (X2) are distributed as a bivariate normal random variable with the parameters µ1 = 1800 hours, µ2 = 0.05 inch, (sigma^2) 1 = 1600 hours2, (sigma^2)2 = 0.04 inch2 , and p = 0.8. The quality-control manager wishes to determine the life of each tube by measuring the filament diameter. If a filament diameter is 0.09, what is the probability that the tube will last 1900 hours?