In Graph x-axis represents number of visits and y-axis represents cost.
As graph comes up to be a linear one, so we can clearly say that cost is increasing linearly in multiples of 5.5 with increase in number of visits.
Example :
If museum is visited once then cost (y) = 5.5 x 1 = 5.5
If museum is visited twice then cost (y) = 5.5 x 2 = 11
If museum is visited thrice then cost (y) = 5.5 x 3 = 16.5
... cost (y) goes on in creasing when number of visits (x) increase with multiples of 5.5
