Expected value and variance of Paul's coin flip game earnings

[dream2rule9]

Paul is playing a game with his friend Peter where Paul tosses a coin and if it comes up heads
Paul gives Peter a dollar and if it comes up tails Peter gives Paul a dollar. Paul plays the
game ten times.
a. What is the expected total earnings for Paul?
b. What is the variance of Paul's total earnings?
c. Suppose that the dice is biased and Paul has a 0.4 chance of winning for each flip.
repeat the calculations in parts a and b?

 

[daveb]

Do you know how to calculate expectation values? If so, just calculate the expected number of tails. Then do the same, but instead of a 0.5 probability of tails, its now 0.4