How many donkeys should the cruise line have in its herd?

A) 8,111
B) 7,977
C) 7,842
D) 7,707

The cruise line should aim to cover the demand for donkey rides up to a certain percentile of the normal distribution of tourist numbers to balance between the fixed cost of maintaining donkeys and the variable cost of renting additional capacity on the spot market. Given the cost structure, it's more economical to cover the majority of demand with owned donkeys and only resort to the spot market for unusually high demand. The correct number of donkeys corresponds to the demand level that optimizes this balance, which, based on the calculation method involving the normal distribution of tourist demand and the costs provided, is closest to the option provided as 7,977.