According to the market survey, the daily tourist volume f(t) (ten thousand people) of a tourist city in the past month (30 days) is related to the time t (days).

Solution: (1) Judging from the meaning of the question,

;

(ii) Because

;

① when 1 ≤ t < 15,

Take the equal sign if and only if, that is, t=5.

② When 15≤t≤30,

It can be proved that w(t) monotonically decreases on t ∈ [15,30],

So when t=30, the minimum value of w(t) is

,

Therefore, the minimum daily income of tourism in this city is 1 10,000 yuan.