Answer:
Expected winnings for one spin = 0.1
Step-by-step explanation:
Expected Value = Sum of [(Probability of X)(Value of X)]
E(X) = Σ [P(X).X]
Two Events : X = +68 , P(X) = 1/38 and X = -2 , P(X) = 37/38
E(X) = [(68) (1/38)] + [(-2)(37/38)]
[(68)(0.03)] + [(-2)(0.97)]
= 2.04 - 1.94
= 0.1
The part D is the correct one...
1. we know she needs 3 packs of biscuits
2. Shop A you only need to pay for 2 packs
3. Shop B you only need to pay for 2 packs
4. Shop C you need to pay for all three
5. so we know C is out of the option.

so shop A and B will cost the least