An enterprising MBA graduate who has been unable to find gainful employment has taken to visiting an office block in town each lunchtime with an array of freshly made sandwiches for sale. The graduate reckons that he has a 90 per cent chance of selling a sandwich to any of the people working in the office block. He visits one office with 12 employees.

(a) Calculate the probability distribution of sandwich sales.

(b) Calculate the mean number of sales.

(c) How might the graduate use this information to improve the profitability of his activities?