The manager of the customer service division of a major consumer electronics company is interested in determining whether the customers who have purchased a videocassette recorder over the past 12 months are satisfied with their products.If there are 4 different brands of videocassette recorders made by the company,the best sampling strategy would be to use a:

A) simple random sample.
B) stratified random sample.
C) cluster sample.
D) self-selected sample.

Refer to Mary Lee. If Mary Lee paid $20 per share for her preferred stock, and if common stock was selling at $50 per share on the date of conversion, compute the amount that Mary Lee's investment increased in value.​