A product's demand per period follows a normal distribution with mean of 60 and standard deviation of 10. The lead time is 2 periods What order-up-to level should be used to achieve at least a 95% in- stock probability?
a) 137
b) 149
c) 209

White shapes and black shapes are used in a game. some of the shapes are circles. while the rest are squares. the ratio of the number of white shapes to the number of black shapes is 5: 11. the ratio of the number of white cicrles to the number of white squares is 3: 7. the ratio of the number of black circles to the number of black squres is 3: 8. work out what fraction of all the shapes are circles.