Please solve above using R program

(b) Bayesian analysis using the default prior: i. Calculate an approximate posterior probability that the mean speed decreased after the sign was posted. ii. Calculate an approximate 90% credible interval for the decrease in mean speed after the sign is posted. (c) Do you think the mean speed was lower after the sign was placed? Why or why not? (b) Bayesian analysis using the default prior: i. Calculate an approximate posterior probability that the mean speed decreased after the sign was posted. ii. Calculate an approximate 90% credible interval for the decrease in mean speed after the sign is posted. (c) Do you think the mean speed was lower after the sign was placed? Why or why not