The graph shows the number of calls (n) Pete made on his mobile phone each month last year and his bill (£b) for the month.

1. Write down the equation of the line of best fit.

b= ?n + ?

2. What is the average cost of each extra call Pete makes?

cost= ? pence

3. Estimate how much Pete would pay in a month when he made 40 calls.

Cost= £?