Answer:
The answer is "Option a".
Step-by-step explanation:
Using the binomial distribution:

In this the maximum value which is significantly low,
, and the minimum value which is significantly high,
, that is equal to:

They increased it by $10.
It ended up costing $60.
Hope this helps.
0.5 is the first way
1/2 is the second way
50% is the third way.
Hope that helps bud :).