It was reported that 52% of families purchase online during black Friday last year. This year, 1400 families were randomly sampled. the survey found that 760 families purchased online during the black Friday.

a. [4] Calculate the 99% CI for the true population proportion of online purchase during the black Friday this year.

b. [3] If we request the bound on the error of estimation to be 0.06 for a 95% CI, using the sample information given in the question as the prior experience, find the minimum sample size