You are responsible for detecting the source of the error when a computer system fails. From your analysis you know that the source of error is the disk drive, the computer memory, or the operating system. You know that $50 \%$ of the errors are disk drive errors, $30 \%$ are computer memory errors, and the remainder are operating system errors. From the component performance standards, you know that when a disk drive error occurs, the probability of failure is $0.60$; when a computer memory error occurs, the probability of failure is $0.7$; and when an operating system error occurs, the probability of failure is $0.3$. Given the information from the component performance standards, what is the probability of a disk drive error, given that a failure occurred?