<image>(2014 Autumn • Tai Jiang District school-level final) Given the domain of the function f(x) as [-1, 5], with some corresponding values as shown in the table below, the graph of the derivative function y = f′(x) is as shown in the image. Regarding the following propositions about f(x):

\frac{}① The function f(x) has a local minimum at x = 2;
② The function f(x) is decreasing on the interval [0, 2];
③ If the maximum value of f(x) when x ∈ [-1, t] is 3, then the maximum value of t is 5;
④ There are _____ correct propositions out of these.

Number of correct propositions: _____