can you help me with this using R:

Suppose I want to know if a six-sided die is a fair die (all six sides equally likely, with probability 1/6). I have reason to suspect it is a loaded (weighted) die, where '6' is more likely to come up. I roll the die 80 times and get 24 rolls of '6'. a) How many rolls of '6' would we expect over those 80 rolls if it was a fair six-sided die? b) Is there sufficient evidence to say the die is unfair, using an exact test? On what p-value is your decision based?