The daily sales in a retail store can be well approximated by a mixture of normal probability distributions. There is a 0.4 probability that the sales follow a normal distribution with mean $10,000 and std dev $1000. There is a 0.3 probability that the sales follow a normal distribution with mean $12,000 and std dev $1000 and there is a 0.3 probability that it follows normal distribution with mean $14,000 and std dev $1500. 
For a randomly selected day, what is the probability that sales are greater than or equal to $12,000?  
[HINT: Separately calculate the probabilities of sales being greater than $12,000 using each of the three Normal distributions and then combine those calculated probabilities using the weights given (0.4, 0.3 and 0.3)]
