A hardware store sells tubs of paint. Each tub is advertised as containing no less than 1.50 litres. A sample of 20 tubs is selected; the sample mean and standard deviation were determined to be 1.41 and 0.26, respectively. If the goal is to test whether the average content is less than 1.50 litres, what is the minimum value of the sample mean needed to reject the null hypothesis at a 10% level of significance?