Answer
Since the consequences of concluding that people spend more when using a credit card when, in fact, it is not true are not severe, it would be legitimate to change the level to $α=0.05$
Work Step by Step
According to item (b), $t_0=2.247$
$t_α=t_{0.05}=1.833$
(According to Table VI, for d.f. = 9 and area in right tail = 0.05)
Now, $t_0\gt t_α$ and we can reject the null hypothesis.
