A Spanish professor assigns letter grades on a test according to the following scheme.

A: Top 9% of scores

B: Scores below the top 9% and above the bottom 60%

C: Scores below the top 40% and above the bottom 22%

D: Scores below the top 78% and above the bottom 6%

F: Bottom 6% of scores

Scores on the test are normally distributed with a mean of 77.8 and a standard deviation of 9.1. Find the score for the lowest B grade.