Answer: $85,000
Step-by-step explanation:
Given : In a given population of two-earner male-female couples, male earnings have a mean of $40,000 per year and a standard deviation of $12,000.

Female earnings have a mean of $45,000 per year and a standard deviation of $18,000.

If C denote the combined earnings for a randomly selected couple.
Then, the mean of C will be :-

Hence, the mean of C = $85,000
Answer: A, B, C.
If the stack of cards are shifted so it is not straight, it still has everything the same.
The formula to calculate standard deviation from probability is \sqrt(n*p*(1-p)). n is the sample size, and 200 in this case (number of putts for practice). p is 80% or 0.8, the probability that he can make it. So the standard deviation is \sqrt(200*0.8*(1-0.8)=\sqrt(200*0.8*0.2)=\sqrt(16)=4.
1.33333333333333333333333333333333333333333333333
or 1.33