Lifetimes of electronic components can often be modeled by an exponential model. Suppose quality control engineers want to model the lifetime of a hard drive to have a mean lifetime of 4 years. Complete parts a and b below. a) What value of should they use? at They should use a value of ford. (Type an integer or a fraction.) olib) With this model, what would the probability be that a hard drive fasts 7 years or less? The probability is ec (Type an integer or a decimal. Round to three decimal places as needed.) ma