A state energy agency mailed questionnaires on energy conservation to 1,000 homeowners in the state capital. Five hundred questionnaires were returned. Suppose an experiment consists of randomly selecting one of the returned questionnaires. Consider the events: A: {The home is constructed of brick}
B: {The home is more than 30 years old}
In terms of A and B, describe a home that is constructed of brick and is less than or equal to 30 years old.
A ∩ Bc
A ∩ B
(A ∩ B)c
A ∪ B

Compare these two waves: the blue and orange waves have the same pitch, but the blue wave is louder. the blue and orange waves have the same volume, but the blue wave has a higher pitch. the orange wave has a higher pitch, but the blue wave is louder. the blue wave has a higher pitch, but the orange wave is louder.

What does independent variable and dependent variable mean in math?

The management of a supermarket wants to adopt a new promotional policy of giving a free gift to every customer who spends more than a certain amount per visit at this supermarket. the expectation of the management is that after this promotional policy is advertised, the expenditures for all customers at this supermarket will be normally distributed with a mean of $95 and a standard deviation of $20. if the management wants to give free gifts to at most 10% of the customers, what should the amount be above which a customer would receive a free gift?