4.(30pt} 4.a 4.b 4.c The data in MYEL.csv contains survival times for 25 patients diagnosed with magma al., 1977). The patients were randomly assigned to two drug treatments. The variables are as follows: DUR is the time in days from the point of randomization to either death or censoring (which could occur either by loss to follow up or termination of the observation). STATUS has a value of 1 if dead and a value off! if censored. TREAT species a value of 1 or 2 to correspond to the two treatments. RENAL has a value of 1 if renal functioning was normal at the time of randomization; it has a value of D for impaired functioning. How many levels are there in each factor variable? Does the survival time differ by STATUS? Does the survival time differ by treatment?