A husband and wife open a start-up tech company in Miami. The wife is the CEO and the husband is the VP of product. Both husband and wife go on different sales meetings because they don’t have enough time to conduct sales together and they need to show their investors that there is a demand in the marketplace for their services. Let X be the number of sales the wife completes in a month and Y be the number of sales that the husband completes in a month. Assuming that μ_x=5 and μ_y=7, what is the mean of z, the total number of sales per month?