Answer
Fail to reject the null hypothesis.
Work Step by Step
$H_{0}:\mu_d=0,$ $H_{a}:\mu_d$ is less than 0. The test statistic is:$t=\frac{\overline{d}-\mu_d}{s_d/\sqrt{n}}=\frac{-1.57-0}{4.5957/\sqrt{10}}=-1.08.$ The P is the corresponding probability using the table with df=10-1=9, hence P is more than 0.1. If the P-value is less than $\alpha$, which is the significance level, then this means the rejection of the null hypothesis. Hence:P is more than $\alpha=0.05$, hence we fail to reject the null hypothesis. Hence there doesn't seem to be difference in sales.
