The companies that are the prime purchasers of computer software will not buy a software package if the costs of training staff to use it are high, and we know that it is expensive to teach people a software package that demands the memorization of unfamiliar commands. As a result, to be successful, commercial computer software cannot require users to memorize unfamiliar commands. The conclusion above follows logically if which one of the following is assumed? ['The more difficult it is to learn how to use a piece of software, the more expensive it is to teach a person to use that software.', 'If the initial cost of computer software is high, but the cost of training users is low, prime purchasers will still buy that software.', 'Commercial computer software will not be successful unless prime purchasers buy it.', 'If most prime purchasers of computer software buy a software product, that product will be successful.']