7.5. ** Two students measure a resistance by different methods. Each makes 10 measurements and computes the mean and its standard deviation, and their final results are as follows: Student A: R = 72 + 8 ohms Student B: R = 78 + 5 ohms. (a) Including both measurements, what are the best estimate of R and its uncer- tainty? (b) Approximately how many measurements (using his same technique) would student A need to make to give his result the same weight as B's? (Remember that each student's final uncertainty is the SDOM, which is equal to the SD/VN.)