4. (30 points) A manufacmring process produces a mix of \"good" and \" had\" memory chips. Lifetime (T) of good chips follows an exponential distribution with a rate of failure a. {i.e.fr(t)= me '1'). Lifetime of bad chips is also exponentially distributed, with failure rate 1000 a. The fraction of \"bad\" chips is p. A chip is selected at random. Event F = {(chip functioning at t (T > t)} Event B = (Chip selected is \"bad\") Event G = (Chip selected is \"good") a) (4 points) Sketch the pdfs for lifetime of \"good\" and \"had\" chips fr(t)