The sales data from the past two months of a frozen yogurt shop are approximately normal

The sales data from the past two months of a frozen yogurt shop are approximately normal. 

The mean daily sales for the first month was $200 with a standard deviation of $30. On the 15th of the first month, the shop sold $245 of yogurt. 

The mean daily sales for the second month was $220 with a standard deviation of $50. On the 15th of the second month, the shop sold $270 of yogurt.

Which month had a higher z-score for sales on the 15th, and what is the value of that z-score?

• a.)The first month, with a z-score of 1.5.
   
• b.)The second month, with a score of 1.67.
• c.)The second month, with a z-score of 1.
• d.)The first month, with a score of 0.9.